[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Emacs-diffs] Changes to cl.texi
|
From: |
Glenn Morris |
|
Subject: |
[Emacs-diffs] Changes to cl.texi |
|
Date: |
Thu, 06 Sep 2007 04:34:29 +0000 |
CVSROOT: /sources/emacs
Module name: emacs
Changes by: Glenn Morris <gm> 07/09/06 04:34:29
Index: cl.texi
===================================================================
RCS file: cl.texi
diff -N cl.texi
--- cl.texi 15 Apr 2007 20:57:14 -0000 1.33
+++ /dev/null 1 Jan 1970 00:00:00 -0000
@@ -1,5377 +0,0 @@
-\input texinfo @c -*-texinfo-*-
address@hidden ../info/cl
address@hidden Common Lisp Extensions
-
address@hidden
-This file documents the GNU Emacs Common Lisp emulation package.
-
-Copyright @copyright{} 1993, 2001, 2002, 2003, 2004, 2005, 2006, 2007
-Free Software Foundation, Inc.
-
address@hidden
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.2 or
-any later version published by the Free Software Foundation; with no
-Invariant Sections, with the Front-Cover texts being ``A GNU
-Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
-license is included in the section entitled ``GNU Free Documentation
-License'' in the Emacs manual.
-
-(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
-this GNU Manual, like GNU software. Copies published by the Free
-Software Foundation raise funds for GNU development.''
-
-This document is part of a collection distributed under the GNU Free
-Documentation License. If you want to distribute this document
-separately from the collection, you can do so by adding a copy of the
-license to the document, as described in section 6 of the license.
address@hidden quotation
address@hidden copying
-
address@hidden Emacs
address@hidden
-* CL: (cl). Partial Common Lisp support for Emacs Lisp.
address@hidden direntry
-
address@hidden
-
address@hidden
address@hidden 6
address@hidden @titlefont{Common Lisp Extensions}
address@hidden 4
address@hidden For GNU Emacs Lisp
address@hidden 1
address@hidden Version 2.02
address@hidden 5
address@hidden Dave Gillespie
address@hidden daveg@@synaptics.com
address@hidden
address@hidden 0pt plus 1filll
address@hidden
address@hidden titlepage
-
address@hidden Top, Overview, (dir), (dir)
address@hidden Introduction
-
address@hidden
-This document describes a set of Emacs Lisp facilities borrowed from
-Common Lisp. All the facilities are described here in detail. While
-this document does not assume any prior knowledge of Common Lisp, it
-does assume a basic familiarity with Emacs Lisp.
-
address@hidden
-* Overview:: Installation, usage, etc.
-* Program Structure:: Arglists, `eval-when', `defalias'
-* Predicates:: `typep', `eql', and `equalp'
-* Control Structure:: `setf', `do', `loop', etc.
-* Macros:: Destructuring, `define-compiler-macro'
-* Declarations:: `proclaim', `declare', etc.
-* Symbols:: Property lists, `gensym'
-* Numbers:: Predicates, functions, random numbers
-* Sequences:: Mapping, functions, searching, sorting
-* Lists:: `cadr', `sublis', `member*', `assoc*', etc.
-* Structures:: `defstruct'
-* Assertions:: `check-type', `assert', `ignore-errors'.
-
-* Efficiency Concerns:: Hints and techniques
-* Common Lisp Compatibility:: All known differences with Steele
-* Old CL Compatibility:: All known differences with old cl.el
-* Porting Common Lisp:: Hints for porting Common Lisp code
-
-* GNU Free Documentation License:: The license for this documentation.
-* Function Index::
-* Variable Index::
address@hidden menu
-
address@hidden Overview, Program Structure, Top, Top
address@hidden
address@hidden Overview
address@hidden ifnottex
-
address@hidden
-Common Lisp is a huge language, and Common Lisp systems tend to be
-massive and extremely complex. Emacs Lisp, by contrast, is rather
-minimalist in the choice of Lisp features it offers the programmer.
-As Emacs Lisp programmers have grown in number, and the applications
-they write have grown more ambitious, it has become clear that Emacs
-Lisp could benefit from many of the conveniences of Common Lisp.
-
-The @dfn{CL} package adds a number of Common Lisp functions and
-control structures to Emacs Lisp. While not a 100% complete
-implementation of Common Lisp, @dfn{CL} adds enough functionality
-to make Emacs Lisp programming significantly more convenient.
-
address@hidden note:} the @dfn{CL} functions are not standard parts of
-the Emacs Lisp name space, so it is legitimate for users to define
-them with other, conflicting meanings. To avoid conflicting with
-those user activities, we have a policy that packages installed in
-Emacs must not load @dfn{CL} at run time. (It is ok for them to load
address@hidden at compile time only, with @code{eval-when-compile}, and use
-the macros it provides.) If you are writing packages that you plan to
-distribute and invite widespread use for, you might want to observe
-the same rule.
-
-Some Common Lisp features have been omitted from this package
-for various reasons:
-
address@hidden @bullet
address@hidden
-Some features are too complex or bulky relative to their benefit
-to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
-examples of this group.
-
address@hidden
-Other features cannot be implemented without modification to the
-Emacs Lisp interpreter itself, such as multiple return values,
-lexical scoping, case-insensitive symbols, and complex numbers.
-The @dfn{CL} package generally makes no attempt to emulate these
-features.
-
address@hidden
-Some features conflict with existing things in Emacs Lisp. For
-example, Emacs' @code{assoc} function is incompatible with the
-Common Lisp @code{assoc}. In such cases, this package usually
-adds the suffix @samp{*} to the function name of the Common
-Lisp version of the function (e.g., @code{assoc*}).
address@hidden itemize
-
-The package described here was written by Dave Gillespie,
address@hidden@@synaptics.com}. It is a total rewrite of the original
-1986 @file{cl.el} package by Cesar Quiroz. Most features of the
-Quiroz package have been retained; any incompatibilities are
-noted in the descriptions below. Care has been taken in this
-version to ensure that each function is defined efficiently,
-concisely, and with minimal impact on the rest of the Emacs
-environment.
-
address@hidden
-* Usage:: How to use the CL package
-* Organization:: The package's five component files
-* Installation:: Compiling and installing CL
-* Naming Conventions:: Notes on CL function names
address@hidden menu
-
address@hidden Usage, Organization, Overview, Overview
address@hidden Usage
-
address@hidden
-Lisp code that uses features from the @dfn{CL} package should
-include at the beginning:
-
address@hidden
-(require 'cl)
address@hidden example
-
address@hidden
-If you want to ensure that the new (Gillespie) version of @dfn{CL}
-is the one that is present, add an additional @code{(require 'cl-19)}
-call:
-
address@hidden
-(require 'cl)
-(require 'cl-19)
address@hidden example
-
address@hidden
-The second call will fail (with address@hidden not found'') if
-the old @file{cl.el} package was in use.
-
-It is safe to arrange to load @dfn{CL} at all times, e.g.,
-in your @file{.emacs} file. But it's a good idea, for portability,
-to @code{(require 'cl)} in your code even if you do this.
-
address@hidden Organization, Installation, Usage, Overview
address@hidden Organization
-
address@hidden
-The Common Lisp package is organized into four files:
-
address@hidden @file
address@hidden cl.el
-This is the ``main'' file, which contains basic functions
-and information about the package. This file is relatively
-compact---about 700 lines.
-
address@hidden cl-extra.el
-This file contains the larger, more complex or unusual functions.
-It is kept separate so that packages which only want to use Common
-Lisp fundamentals like the @code{cadr} function won't need to pay
-the overhead of loading the more advanced functions.
-
address@hidden cl-seq.el
-This file contains most of the advanced functions for operating
-on sequences or lists, such as @code{delete-if} and @code{assoc*}.
-
address@hidden cl-macs.el
-This file contains the features of the packages which are macros
-instead of functions. Macros expand when the caller is compiled,
-not when it is run, so the macros generally only need to be
-present when the byte-compiler is running (or when the macros are
-used in uncompiled code such as a @file{.emacs} file). Most of
-the macros of this package are isolated in @file{cl-macs.el} so
-that they won't take up memory unless you are compiling.
address@hidden table
-
-The file @file{cl.el} includes all necessary @code{autoload}
-commands for the functions and macros in the other three files.
-All you have to do is @code{(require 'cl)}, and @file{cl.el}
-will take care of pulling in the other files when they are
-needed.
-
-There is another file, @file{cl-compat.el}, which defines some
-routines from the older @file{cl.el} package that are no longer
-present in the new package. This includes internal routines
-like @code{setelt} and @code{zip-lists}, deprecated features
-like @code{defkeyword}, and an emulation of the old-style
-multiple-values feature. @xref{Old CL Compatibility}.
-
address@hidden Installation, Naming Conventions, Organization, Overview
address@hidden Installation
-
address@hidden
-Installation of the @dfn{CL} package is simple: Just put the
-byte-compiled files @file{cl.elc}, @file{cl-extra.elc},
address@hidden, @file{cl-macs.elc}, and @file{cl-compat.elc}
-into a directory on your @code{load-path}.
-
-There are no special requirements to compile this package:
-The files do not have to be loaded before they are compiled,
-nor do they need to be compiled in any particular order.
-
-You may choose to put the files into your main @file{lisp/}
-directory, replacing the original @file{cl.el} file there. Or,
-you could put them into a directory that comes before @file{lisp/}
-on your @code{load-path} so that the old @file{cl.el} is
-effectively hidden.
-
-Also, format the @file{cl.texinfo} file and put the resulting
-Info files in the @file{info/} directory or another suitable place.
-
-You may instead wish to leave this package's components all in
-their own directory, and then add this directory to your
address@hidden and @code{Info-directory-list}.
-Add the directory to the front of the list so the old @dfn{CL}
-package and its documentation are hidden.
-
address@hidden Naming Conventions, , Installation, Overview
address@hidden Naming Conventions
-
address@hidden
-Except where noted, all functions defined by this package have the
-same names and calling conventions as their Common Lisp counterparts.
-
-Following is a complete list of functions whose names were changed
-from Common Lisp, usually to avoid conflicts with Emacs. In each
-case, a @samp{*} has been appended to the Common Lisp name to obtain
-the Emacs name:
-
address@hidden
-defun* defsubst* defmacro* function*
-member* assoc* rassoc* get*
-remove* delete* mapcar* sort*
-floor* ceiling* truncate* round*
-mod* rem* random*
address@hidden example
-
-Internal function and variable names in the package are prefixed
-by @code{cl-}. Here is a complete list of functions @emph{not}
-prefixed by @code{cl-} which were not taken from Common Lisp:
-
address@hidden
-floatp-safe lexical-let lexical-let*
-callf callf2 letf letf*
-defsubst*
address@hidden example
-
-The following simple functions and macros are defined in @file{cl.el};
-they do not cause other components like @file{cl-extra} to be loaded.
-
address@hidden
-eql floatp-safe endp
-evenp oddp plusp minusp
-caaar .. cddddr
-list* ldiff rest first .. tenth
-copy-list subst mapcar* [2]
-adjoin [3] acons pairlis pop [4]
-push [4] pushnew [3,4] incf [4] decf [4]
-proclaim declaim
address@hidden example
-
address@hidden
-[2] Only for one sequence argument or two list arguments.
-
address@hidden
-[3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
-and @code{:key} is not used.
-
address@hidden
-[4] Only when @var{place} is a plain variable name.
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Program Structure, Predicates, Overview, Top
address@hidden Program Structure
-
address@hidden
-This section describes features of the @dfn{CL} package which have to
-do with programs as a whole: advanced argument lists for functions,
-and the @code{eval-when} construct.
-
address@hidden
-* Argument Lists:: `&key', `&aux', `defun*', `defmacro*'.
-* Time of Evaluation:: The `eval-when' construct.
address@hidden menu
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Argument Lists, Time of Evaluation, Program Structure, Program
Structure
address@hidden Argument Lists
-
address@hidden
-Emacs Lisp's notation for argument lists of functions is a subset of
-the Common Lisp notation. As well as the familiar @code{&optional}
-and @code{&rest} markers, Common Lisp allows you to specify default
-values for optional arguments, and it provides the additional markers
address@hidden&key} and @code{&aux}.
-
-Since argument parsing is built-in to Emacs, there is no way for
-this package to implement Common Lisp argument lists seamlessly.
-Instead, this package defines alternates for several Lisp forms
-which you must use if you need Common Lisp argument lists.
-
address@hidden defun* name arglist body...
-This form is identical to the regular @code{defun} form, except
-that @var{arglist} is allowed to be a full Common Lisp argument
-list. Also, the function body is enclosed in an implicit block
-called @var{name}; @pxref{Blocks and Exits}.
address@hidden defspec
-
address@hidden defsubst* name arglist body...
-This is just like @code{defun*}, except that the function that
-is defined is automatically proclaimed @code{inline}, i.e.,
-calls to it may be expanded into in-line code by the byte compiler.
-This is analogous to the @code{defsubst} form;
address@hidden uses a different method (compiler macros) which
-works in all version of Emacs, and also generates somewhat more
-efficient inline expansions. In particular, @code{defsubst*}
-arranges for the processing of keyword arguments, default values,
-etc., to be done at compile-time whenever possible.
address@hidden defspec
-
address@hidden defmacro* name arglist body...
-This is identical to the regular @code{defmacro} form,
-except that @var{arglist} is allowed to be a full Common Lisp
-argument list. The @code{&environment} keyword is supported as
-described in Steele. The @code{&whole} keyword is supported only
-within destructured lists (see below); top-level @code{&whole}
-cannot be implemented with the current Emacs Lisp interpreter.
-The macro expander body is enclosed in an implicit block called
address@hidden
address@hidden defspec
-
address@hidden function* symbol-or-lambda
-This is identical to the regular @code{function} form,
-except that if the argument is a @code{lambda} form then that
-form may use a full Common Lisp argument list.
address@hidden defspec
-
-Also, all forms (such as @code{defsetf} and @code{flet}) defined
-in this package that include @var{arglist}s in their syntax allow
-full Common Lisp argument lists.
-
-Note that it is @emph{not} necessary to use @code{defun*} in
-order to have access to most @dfn{CL} features in your function.
-These features are always present; @code{defun*}'s only
-difference from @code{defun} is its more flexible argument
-lists and its implicit block.
-
-The full form of a Common Lisp argument list is
-
address@hidden
-(@var{var}...
- &optional (@var{var} @var{initform} @var{svar})...
- &rest @var{var}
- &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
- &aux (@var{var} @var{initform})...)
address@hidden example
-
-Each of the five argument list sections is optional. The @var{svar},
address@hidden, and @var{keyword} parts are optional; if they are
-omitted, then @samp{(@var{var})} may be written simply @address@hidden
-
-The first section consists of zero or more @dfn{required} arguments.
-These arguments must always be specified in a call to the function;
-there is no difference between Emacs Lisp and Common Lisp as far as
-required arguments are concerned.
-
-The second section consists of @dfn{optional} arguments. These
-arguments may be specified in the function call; if they are not,
address@hidden specifies the default value used for the argument.
-(No @var{initform} means to use @code{nil} as the default.) The
address@hidden is evaluated with the bindings for the preceding
-arguments already established; @code{(a &optional (b (1+ a)))}
-matches one or two arguments, with the second argument defaulting
-to one plus the first argument. If the @var{svar} is specified,
-it is an auxiliary variable which is bound to @code{t} if the optional
-argument was specified, or to @code{nil} if the argument was omitted.
-If you don't use an @var{svar}, then there will be no way for your
-function to tell whether it was called with no argument, or with
-the default value passed explicitly as an argument.
-
-The third section consists of a single @dfn{rest} argument. If
-more arguments were passed to the function than are accounted for
-by the required and optional arguments, those extra arguments are
-collected into a list and bound to the ``rest'' argument variable.
-Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp.
-Common Lisp accepts @code{&body} as a synonym for @code{&rest} in
-macro contexts; this package accepts it all the time.
-
-The fourth section consists of @dfn{keyword} arguments. These
-are optional arguments which are specified by name rather than
-positionally in the argument list. For example,
-
address@hidden
-(defun* foo (a &optional b &key c d (e 17)))
address@hidden example
-
address@hidden
-defines a function which may be called with one, two, or more
-arguments. The first two arguments are bound to @code{a} and
address@hidden in the usual way. The remaining arguments must be
-pairs of the form @code{:c}, @code{:d}, or @code{:e} followed
-by the value to be bound to the corresponding argument variable.
-(Symbols whose names begin with a colon are called @dfn{keywords},
-and they are self-quoting in the same way as @code{nil} and
address@hidden)
-
-For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five
-arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword
-appears more than once in the function call, the first occurrence
-takes precedence over the later ones. Note that it is not possible
-to specify keyword arguments without specifying the optional
-argument @code{b} as well, since @code{(foo 1 :c 2)} would bind
address@hidden to the keyword @code{:c}, then signal an error because
address@hidden is not a valid keyword.
-
-If a @var{keyword} symbol is explicitly specified in the argument
-list as shown in the above diagram, then that keyword will be
-used instead of just the variable name prefixed with a colon.
-You can specify a @var{keyword} symbol which does not begin with
-a colon at all, but such symbols will not be self-quoting; you
-will have to quote them explicitly with an apostrophe in the
-function call.
-
-Ordinarily it is an error to pass an unrecognized keyword to
-a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask
-Lisp to ignore unrecognized keywords, either by adding the
-marker @code{&allow-other-keys} after the keyword section
-of the argument list, or by specifying an @code{:allow-other-keys}
-argument in the call whose value is address@hidden If the
-function uses both @code{&rest} and @code{&key} at the same time,
-the ``rest'' argument is bound to the keyword list as it appears
-in the call. For example:
-
address@hidden
-(defun* find-thing (thing &rest rest &key need &allow-other-keys)
- (or (apply 'member* thing thing-list :allow-other-keys t rest)
- (if need (error "Thing not found"))))
address@hidden smallexample
-
address@hidden
-This function takes a @code{:need} keyword argument, but also
-accepts other keyword arguments which are passed on to the
address@hidden function. @code{allow-other-keys} is used to
-keep both @code{find-thing} and @code{member*} from complaining
-about each others' keywords in the arguments.
-
-The fifth section of the argument list consists of @dfn{auxiliary
-variables}. These are not really arguments at all, but simply
-variables which are bound to @code{nil} or to the specified
address@hidden during execution of the function. There is no
-difference between the following two functions, except for a
-matter of stylistic taste:
-
address@hidden
-(defun* foo (a b &aux (c (+ a b)) d)
- @var{body})
-
-(defun* foo (a b)
- (let ((c (+ a b)) d)
- @var{body}))
address@hidden example
-
-Argument lists support @dfn{destructuring}. In Common Lisp,
-destructuring is only allowed with @code{defmacro}; this package
-allows it with @code{defun*} and other argument lists as well.
-In destructuring, any argument variable (@var{var} in the above
-diagram) can be replaced by a list of variables, or more generally,
-a recursive argument list. The corresponding argument value must
-be a list whose elements match this recursive argument list.
-For example:
-
address@hidden
-(defmacro* dolist ((var listform &optional resultform)
- &rest body)
- ...)
address@hidden example
-
-This says that the first argument of @code{dolist} must be a list
-of two or three items; if there are other arguments as well as this
-list, they are stored in @code{body}. All features allowed in
-regular argument lists are allowed in these recursive argument lists.
-In addition, the clause @samp{&whole @var{var}} is allowed at the
-front of a recursive argument list. It binds @var{var} to the
-whole list being matched; thus @code{(&whole all a b)} matches
-a list of two things, with @code{a} bound to the first thing,
address@hidden bound to the second thing, and @code{all} bound to the
-list itself. (Common Lisp allows @code{&whole} in top-level
address@hidden argument lists as well, but Emacs Lisp does not
-support this usage.)
-
-One last feature of destructuring is that the argument list may be
-dotted, so that the argument list @code{(a b . c)} is functionally
-equivalent to @code{(a b &rest c)}.
-
-If the optimization quality @code{safety} is set to 0
-(@pxref{Declarations}), error checking for wrong number of
-arguments and invalid keyword arguments is disabled. By default,
-argument lists are rigorously checked.
-
address@hidden Time of Evaluation, , Argument Lists, Program Structure
address@hidden Time of Evaluation
-
address@hidden
-Normally, the byte-compiler does not actually execute the forms in
-a file it compiles. For example, if a file contains @code{(setq foo t)},
-the act of compiling it will not actually set @code{foo} to @code{t}.
-This is true even if the @code{setq} was a top-level form (i.e., not
-enclosed in a @code{defun} or other form). Sometimes, though, you
-would like to have certain top-level forms evaluated at compile-time.
-For example, the compiler effectively evaluates @code{defmacro} forms
-at compile-time so that later parts of the file can refer to the
-macros that are defined.
-
address@hidden eval-when (situations...) forms...
-This form controls when the body @var{forms} are evaluated.
-The @var{situations} list may contain any set of the symbols
address@hidden, @code{load}, and @code{eval} (or their long-winded
-ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel},
-and @code{:execute}).
-
-The @code{eval-when} form is handled differently depending on
-whether or not it is being compiled as a top-level form.
-Specifically, it gets special treatment if it is being compiled
-by a command such as @code{byte-compile-file} which compiles files
-or buffers of code, and it appears either literally at the
-top level of the file or inside a top-level @code{progn}.
-
-For compiled top-level @code{eval-when}s, the body @var{forms} are
-executed at compile-time if @code{compile} is in the @var{situations}
-list, and the @var{forms} are written out to the file (to be executed
-at load-time) if @code{load} is in the @var{situations} list.
-
-For non-compiled-top-level forms, only the @code{eval} situation is
-relevant. (This includes forms executed by the interpreter, forms
-compiled with @code{byte-compile} rather than @code{byte-compile-file},
-and non-top-level forms.) The @code{eval-when} acts like a
address@hidden if @code{eval} is specified, and like @code{nil}
-(ignoring the body @var{forms}) if not.
-
-The rules become more subtle when @code{eval-when}s are nested;
-consult Steele (second edition) for the gruesome details (and
-some gruesome examples).
-
-Some simple examples:
-
address@hidden
-;; Top-level forms in foo.el:
-(eval-when (compile) (setq foo1 'bar))
-(eval-when (load) (setq foo2 'bar))
-(eval-when (compile load) (setq foo3 'bar))
-(eval-when (eval) (setq foo4 'bar))
-(eval-when (eval compile) (setq foo5 'bar))
-(eval-when (eval load) (setq foo6 'bar))
-(eval-when (eval compile load) (setq foo7 'bar))
address@hidden example
-
-When @file{foo.el} is compiled, these variables will be set during
-the compilation itself:
-
address@hidden
-foo1 foo3 foo5 foo7 ; `compile'
address@hidden example
-
-When @file{foo.elc} is loaded, these variables will be set:
-
address@hidden
-foo2 foo3 foo6 foo7 ; `load'
address@hidden example
-
-And if @file{foo.el} is loaded uncompiled, these variables will
-be set:
-
address@hidden
-foo4 foo5 foo6 foo7 ; `eval'
address@hidden example
-
-If these seven @code{eval-when}s had been, say, inside a @code{defun},
-then the first three would have been equivalent to @code{nil} and the
-last four would have been equivalent to the corresponding @code{setq}s.
-
-Note that @code{(eval-when (load eval) @dots{})} is equivalent
-to @code{(progn @dots{})} in all contexts. The compiler treats
-certain top-level forms, like @code{defmacro} (sort-of) and
address@hidden, as if they were wrapped in @code{(eval-when
-(compile load eval) @dots{})}.
address@hidden defspec
-
-Emacs includes two special forms related to @code{eval-when}.
-One of these, @code{eval-when-compile}, is not quite equivalent to
-any @code{eval-when} construct and is described below.
-
-The other form, @code{(eval-and-compile @dots{})}, is exactly
-equivalent to @samp{(eval-when (compile load eval) @dots{})} and
-so is not itself defined by this package.
-
address@hidden eval-when-compile forms...
-The @var{forms} are evaluated at compile-time; at execution time,
-this form acts like a quoted constant of the resulting value. Used
-at top-level, @code{eval-when-compile} is just like @samp{eval-when
-(compile eval)}. In other contexts, @code{eval-when-compile}
-allows code to be evaluated once at compile-time for efficiency
-or other reasons.
-
-This form is similar to the @samp{#.} syntax of true Common Lisp.
address@hidden defspec
-
address@hidden load-time-value form
-The @var{form} is evaluated at load-time; at execution time,
-this form acts like a quoted constant of the resulting value.
-
-Early Common Lisp had a @samp{#,} syntax that was similar to
-this, but ANSI Common Lisp replaced it with @code{load-time-value}
-and gave it more well-defined semantics.
-
-In a compiled file, @code{load-time-value} arranges for @var{form}
-to be evaluated when the @file{.elc} file is loaded and then used
-as if it were a quoted constant. In code compiled by
address@hidden rather than @code{byte-compile-file}, the
-effect is identical to @code{eval-when-compile}. In uncompiled
-code, both @code{eval-when-compile} and @code{load-time-value}
-act exactly like @code{progn}.
-
address@hidden
-(defun report ()
- (insert "This function was executed on: "
- (current-time-string)
- ", compiled on: "
- (eval-when-compile (current-time-string))
- ;; or '#.(current-time-string) in real Common Lisp
- ", and loaded on: "
- (load-time-value (current-time-string))))
address@hidden example
-
address@hidden
-Byte-compiled, the above defun will result in the following code
-(or its compiled equivalent, of course) in the @file{.elc} file:
-
address@hidden
-(setq --temp-- (current-time-string))
-(defun report ()
- (insert "This function was executed on: "
- (current-time-string)
- ", compiled on: "
- '"Wed Jun 23 18:33:43 1993"
- ", and loaded on: "
- --temp--))
address@hidden example
address@hidden defspec
-
address@hidden Predicates, Control Structure, Program Structure, Top
address@hidden Predicates
-
address@hidden
-This section describes functions for testing whether various
-facts are true or false.
-
address@hidden
-* Type Predicates:: `typep', `deftype', and `coerce'
-* Equality Predicates:: `eql' and `equalp'
address@hidden menu
-
address@hidden Type Predicates, Equality Predicates, Predicates, Predicates
address@hidden Type Predicates
-
address@hidden
-The @dfn{CL} package defines a version of the Common Lisp @code{typep}
-predicate.
-
address@hidden typep object type
-Check if @var{object} is of type @var{type}, where @var{type} is a
-(quoted) type name of the sort used by Common Lisp. For example,
address@hidden(typep foo 'integer)} is equivalent to @code{(integerp foo)}.
address@hidden defun
-
-The @var{type} argument to the above function is either a symbol
-or a list beginning with a symbol.
-
address@hidden @bullet
address@hidden
-If the type name is a symbol, Emacs appends @samp{-p} to the
-symbol name to form the name of a predicate function for testing
-the type. (Built-in predicates whose names end in @samp{p} rather
-than @samp{-p} are used when appropriate.)
-
address@hidden
-The type symbol @code{t} stands for the union of all types.
address@hidden(typep @var{object} t)} is always true. Likewise, the
-type symbol @code{nil} stands for nothing at all, and
address@hidden(typep @var{object} nil)} is always false.
-
address@hidden
-The type symbol @code{null} represents the symbol @code{nil}.
-Thus @code{(typep @var{object} 'null)} is equivalent to
address@hidden(null @var{object})}.
-
address@hidden
-The type symbol @code{atom} represents all objects that are not cons
-cells. Thus @code{(typep @var{object} 'atom)} is equivalent to
address@hidden(atom @var{object})}.
-
address@hidden
-The type symbol @code{real} is a synonym for @code{number}, and
address@hidden is a synonym for @code{integer}.
-
address@hidden
-The type symbols @code{character} and @code{string-char} match
-integers in the range from 0 to 255.
-
address@hidden
-The type symbol @code{float} uses the @code{floatp-safe} predicate
-defined by this package rather than @code{floatp}, so it will work
-correctly even in Emacs versions without floating-point support.
-
address@hidden
-The type list @code{(integer @var{low} @var{high})} represents all
-integers between @var{low} and @var{high}, inclusive. Either bound
-may be a list of a single integer to specify an exclusive limit,
-or a @code{*} to specify no limit. The type @code{(integer * *)}
-is thus equivalent to @code{integer}.
-
address@hidden
-Likewise, lists beginning with @code{float}, @code{real}, or
address@hidden represent numbers of that type falling in a particular
-range.
-
address@hidden
-Lists beginning with @code{and}, @code{or}, and @code{not} form
-combinations of types. For example, @code{(or integer (float 0 *))}
-represents all objects that are integers or non-negative floats.
-
address@hidden
-Lists beginning with @code{member} or @code{member*} represent
-objects @code{eql} to any of the following values. For example,
address@hidden(member 1 2 3 4)} is equivalent to @code{(integer 1 4)},
-and @code{(member nil)} is equivalent to @code{null}.
-
address@hidden
-Lists of the form @code{(satisfies @var{predicate})} represent
-all objects for which @var{predicate} returns true when called
-with that object as an argument.
address@hidden itemize
-
-The following function and macro (not technically predicates) are
-related to @code{typep}.
-
address@hidden coerce object type
-This function attempts to convert @var{object} to the specified
address@hidden If @var{object} is already of that type as determined by
address@hidden, it is simply returned. Otherwise, certain types of
-conversions will be made: If @var{type} is any sequence type
-(@code{string}, @code{list}, etc.) then @var{object} will be
-converted to that type if possible. If @var{type} is
address@hidden, then strings of length one and symbols with
-one-character names can be coerced. If @var{type} is @code{float},
-then integers can be coerced in versions of Emacs that support
-floats. In all other circumstances, @code{coerce} signals an
-error.
address@hidden defun
-
address@hidden deftype name arglist forms...
-This macro defines a new type called @var{name}. It is similar
-to @code{defmacro} in many ways; when @var{name} is encountered
-as a type name, the body @var{forms} are evaluated and should
-return a type specifier that is equivalent to the type. The
address@hidden is a Common Lisp argument list of the sort accepted
-by @code{defmacro*}. The type specifier @samp{(@var{name} @var{args}...)}
-is expanded by calling the expander with those arguments; the type
-symbol @address@hidden is expanded by calling the expander with
-no arguments. The @var{arglist} is processed the same as for
address@hidden except that optional arguments without explicit
-defaults use @code{*} instead of @code{nil} as the ``default''
-default. Some examples:
-
address@hidden
-(deftype null () '(satisfies null)) ; predefined
-(deftype list () '(or null cons)) ; predefined
-(deftype unsigned-byte (&optional bits)
- (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits)))))
-(unsigned-byte 8) @equiv{} (integer 0 255)
-(unsigned-byte) @equiv{} (integer 0 *)
-unsigned-byte @equiv{} (integer 0 *)
address@hidden example
-
address@hidden
-The last example shows how the Common Lisp @code{unsigned-byte}
-type specifier could be implemented if desired; this package does
-not implement @code{unsigned-byte} by default.
address@hidden defspec
-
-The @code{typecase} and @code{check-type} macros also use type
-names. @xref{Conditionals}. @xref{Assertions}. The @code{map},
address@hidden, and @code{merge} functions take type-name
-arguments to specify the type of sequence to return. @xref{Sequences}.
-
address@hidden Equality Predicates, , Type Predicates, Predicates
address@hidden Equality Predicates
-
address@hidden
-This package defines two Common Lisp predicates, @code{eql} and
address@hidden
-
address@hidden eql a b
-This function is almost the same as @code{eq}, except that if @var{a}
-and @var{b} are numbers of the same type, it compares them for numeric
-equality (as if by @code{equal} instead of @code{eq}). This makes a
-difference only for versions of Emacs that are compiled with
-floating-point support. Emacs floats are allocated
-objects just like cons cells, which means that @code{(eq 3.0 3.0)}
-will not necessarily be true---if the two @code{3.0}s were allocated
-separately, the pointers will be different even though the numbers are
-the same. But @code{(eql 3.0 3.0)} will always be true.
-
-The types of the arguments must match, so @code{(eql 3 3.0)} is
-still false.
-
-Note that Emacs integers are ``direct'' rather than allocated, which
-basically means @code{(eq 3 3)} will always be true. Thus @code{eq}
-and @code{eql} behave differently only if floating-point numbers are
-involved, and are indistinguishable on Emacs versions that don't
-support floats.
-
-There is a slight inconsistency with Common Lisp in the treatment of
-positive and negative zeros. Some machines, notably those with IEEE
-standard arithmetic, represent @code{+0} and @code{-0} as distinct
-values. Normally this doesn't matter because the standard specifies
-that @code{(= 0.0 -0.0)} should always be true, and this is indeed
-what Emacs Lisp and Common Lisp do. But the Common Lisp standard
-states that @code{(eql 0.0 -0.0)} and @code{(equal 0.0 -0.0)} should
-be false on IEEE-like machines; Emacs Lisp does not do this, and in
-fact the only known way to distinguish between the two zeros in Emacs
-Lisp is to @code{format} them and check for a minus sign.
address@hidden defun
-
address@hidden equalp a b
-This function is a more flexible version of @code{equal}. In
-particular, it compares strings case-insensitively, and it compares
-numbers without regard to type (so that @code{(equalp 3 3.0)} is
-true). Vectors and conses are compared recursively. All other
-objects are compared as if by @code{equal}.
-
-This function differs from Common Lisp @code{equalp} in several
-respects. First, Common Lisp's @code{equalp} also compares
address@hidden case-insensitively, which would be impractical
-in this package since Emacs does not distinguish between integers
-and characters. In keeping with the idea that strings are less
-vector-like in Emacs Lisp, this package's @code{equalp} also will
-not compare strings against vectors of integers.
address@hidden defun
-
-Also note that the Common Lisp functions @code{member} and @code{assoc}
-use @code{eql} to compare elements, whereas Emacs Lisp follows the
-MacLisp tradition and uses @code{equal} for these two functions.
-In Emacs, use @code{member*} and @code{assoc*} to get functions
-which use @code{eql} for comparisons.
-
address@hidden Control Structure, Macros, Predicates, Top
address@hidden Control Structure
-
address@hidden
-The features described in the following sections implement
-various advanced control structures, including the powerful
address@hidden facility and a number of looping and conditional
-constructs.
-
address@hidden
-* Assignment:: The `psetq' form
-* Generalized Variables:: `setf', `incf', `push', etc.
-* Variable Bindings:: `progv', `lexical-let', `flet', `macrolet'
-* Conditionals:: `case', `typecase'
-* Blocks and Exits:: `block', `return', `return-from'
-* Iteration:: `do', `dotimes', `dolist', `do-symbols'
-* Loop Facility:: The Common Lisp `loop' macro
-* Multiple Values:: `values', `multiple-value-bind', etc.
address@hidden menu
-
address@hidden Assignment, Generalized Variables, Control Structure, Control
Structure
address@hidden Assignment
-
address@hidden
-The @code{psetq} form is just like @code{setq}, except that multiple
-assignments are done in parallel rather than sequentially.
-
address@hidden psetq [symbol address@hidden
-This special form (actually a macro) is used to assign to several
-variables simultaneously. Given only one @var{symbol} and @var{form},
-it has the same effect as @code{setq}. Given several @var{symbol}
-and @var{form} pairs, it evaluates all the @var{form}s in advance
-and then stores the corresponding variables afterwards.
-
address@hidden
-(setq x 2 y 3)
-(setq x (+ x y) y (* x y))
-x
- @result{} 5
-y ; @address@hidden was computed after @code{x} was set.}
- @result{} 15
-(setq x 2 y 3)
-(psetq x (+ x y) y (* x y))
-x
- @result{} 5
-y ; @address@hidden was computed before @code{x} was set.}
- @result{} 6
address@hidden example
-
-The simplest use of @code{psetq} is @code{(psetq x y y x)}, which
-exchanges the values of two variables. (The @code{rotatef} form
-provides an even more convenient way to swap two variables;
address@hidden Macros}.)
-
address@hidden always returns @code{nil}.
address@hidden defspec
-
address@hidden Generalized Variables, Variable Bindings, Assignment, Control
Structure
address@hidden Generalized Variables
-
address@hidden
-A ``generalized variable'' or ``place form'' is one of the many places
-in Lisp memory where values can be stored. The simplest place form is
-a regular Lisp variable. But the cars and cdrs of lists, elements
-of arrays, properties of symbols, and many other locations are also
-places where Lisp values are stored.
-
-The @code{setf} form is like @code{setq}, except that it accepts
-arbitrary place forms on the left side rather than just
-symbols. For example, @code{(setf (car a) b)} sets the car of
address@hidden to @code{b}, doing the same operation as @code{(setcar a b)}
-but without having to remember two separate functions for setting
-and accessing every type of place.
-
-Generalized variables are analogous to ``lvalues'' in the C
-language, where @samp{x = a[i]} gets an element from an array
-and @samp{a[i] = x} stores an element using the same notation.
-Just as certain forms like @code{a[i]} can be lvalues in C, there
-is a set of forms that can be generalized variables in Lisp.
-
address@hidden
-* Basic Setf:: `setf' and place forms
-* Modify Macros:: `incf', `push', `rotatef', `letf', `callf', etc.
-* Customizing Setf:: `define-modify-macro', `defsetf', `define-setf-method'
address@hidden menu
-
address@hidden Basic Setf, Modify Macros, Generalized Variables, Generalized
Variables
address@hidden Basic Setf
-
address@hidden
-The @code{setf} macro is the most basic way to operate on generalized
-variables.
-
address@hidden setf [place address@hidden
-This macro evaluates @var{form} and stores it in @var{place}, which
-must be a valid generalized variable form. If there are several
address@hidden and @var{form} pairs, the assignments are done sequentially
-just as with @code{setq}. @code{setf} returns the value of the last
address@hidden
-
-The following Lisp forms will work as generalized variables, and
-so may appear in the @var{place} argument of @code{setf}:
-
address@hidden @bullet
address@hidden
-A symbol naming a variable. In other words, @code{(setf x y)} is
-exactly equivalent to @code{(setq x y)}, and @code{setq} itself is
-strictly speaking redundant now that @code{setf} exists. Many
-programmers continue to prefer @code{setq} for setting simple
-variables, though, purely for stylistic or historical reasons.
-The macro @code{(setf x y)} actually expands to @code{(setq x y)},
-so there is no performance penalty for using it in compiled code.
-
address@hidden
-A call to any of the following Lisp functions:
-
address@hidden
-car cdr caar .. cddddr
-nth rest first .. tenth
-aref elt nthcdr
-symbol-function symbol-value symbol-plist
-get get* getf
-gethash subseq
address@hidden smallexample
-
address@hidden
-Note that for @code{nthcdr} and @code{getf}, the list argument
-of the function must itself be a valid @var{place} form. For
-example, @code{(setf (nthcdr 0 foo) 7)} will set @code{foo} itself
-to 7. Note that @code{push} and @code{pop} on an @code{nthcdr}
-place can be used to insert or delete at any position in a list.
-The use of @code{nthcdr} as a @var{place} form is an extension
-to standard Common Lisp.
-
address@hidden
-The following Emacs-specific functions are also @code{setf}-able.
-
address@hidden
-buffer-file-name marker-position
-buffer-modified-p match-data
-buffer-name mouse-position
-buffer-string overlay-end
-buffer-substring overlay-get
-current-buffer overlay-start
-current-case-table point
-current-column point-marker
-current-global-map point-max
-current-input-mode point-min
-current-local-map process-buffer
-current-window-configuration process-filter
-default-file-modes process-sentinel
-default-value read-mouse-position
-documentation-property screen-height
-extent-data screen-menubar
-extent-end-position screen-width
-extent-start-position selected-window
-face-background selected-screen
-face-background-pixmap selected-frame
-face-font standard-case-table
-face-foreground syntax-table
-face-underline-p window-buffer
-file-modes window-dedicated-p
-frame-height window-display-table
-frame-parameters window-height
-frame-visible-p window-hscroll
-frame-width window-point
-get-register window-start
-getenv window-width
-global-key-binding x-get-cut-buffer
-keymap-parent x-get-cutbuffer
-local-key-binding x-get-secondary-selection
-mark x-get-selection
-mark-marker
address@hidden smallexample
-
-Most of these have directly corresponding ``set'' functions, like
address@hidden for @code{current-local-map}, or @code{goto-char}
-for @code{point}. A few, like @code{point-min}, expand to longer
-sequences of code when they are @code{setf}'d (@code{(narrow-to-region
-x (point-max))} in this case).
-
address@hidden
-A call of the form @code{(substring @var{subplace} @var{n} address@hidden)},
-where @var{subplace} is itself a valid generalized variable whose
-current value is a string, and where the value stored is also a
-string. The new string is spliced into the specified part of the
-destination string. For example:
-
address@hidden
-(setq a (list "hello" "world"))
- @result{} ("hello" "world")
-(cadr a)
- @result{} "world"
-(substring (cadr a) 2 4)
- @result{} "rl"
-(setf (substring (cadr a) 2 4) "o")
- @result{} "o"
-(cadr a)
- @result{} "wood"
-a
- @result{} ("hello" "wood")
address@hidden example
-
-The generalized variable @code{buffer-substring}, listed above,
-also works in this way by replacing a portion of the current buffer.
-
address@hidden
-A call of the form @code{(apply '@var{func} @dots{})} or
address@hidden(apply (function @var{func}) @dots{})}, where @var{func}
-is a @code{setf}-able function whose store function is ``suitable''
-in the sense described in Steele's book; since none of the standard
-Emacs place functions are suitable in this sense, this feature is
-only interesting when used with places you define yourself with
address@hidden or the long form of @code{defsetf}.
-
address@hidden
-A macro call, in which case the macro is expanded and @code{setf}
-is applied to the resulting form.
-
address@hidden
-Any form for which a @code{defsetf} or @code{define-setf-method}
-has been made.
address@hidden itemize
-
-Using any forms other than these in the @var{place} argument to
address@hidden will signal an error.
-
-The @code{setf} macro takes care to evaluate all subforms in
-the proper left-to-right order; for example,
-
address@hidden
-(setf (aref vec (incf i)) i)
address@hidden example
-
address@hidden
-looks like it will evaluate @code{(incf i)} exactly once, before the
-following access to @code{i}; the @code{setf} expander will insert
-temporary variables as necessary to ensure that it does in fact work
-this way no matter what setf-method is defined for @code{aref}.
-(In this case, @code{aset} would be used and no such steps would
-be necessary since @code{aset} takes its arguments in a convenient
-order.)
-
-However, if the @var{place} form is a macro which explicitly
-evaluates its arguments in an unusual order, this unusual order
-will be preserved. Adapting an example from Steele, given
-
address@hidden
-(defmacro wrong-order (x y) (list 'aref y x))
address@hidden example
-
address@hidden
-the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will
-evaluate @var{b} first, then @var{a}, just as in an actual call
-to @code{wrong-order}.
address@hidden defspec
-
address@hidden Modify Macros, Customizing Setf, Basic Setf, Generalized
Variables
address@hidden Modify Macros
-
address@hidden
-This package defines a number of other macros besides @code{setf}
-that operate on generalized variables. Many are interesting and
-useful even when the @var{place} is just a variable name.
-
address@hidden psetf [place address@hidden
-This macro is to @code{setf} what @code{psetq} is to @code{setq}:
-When several @var{place}s and @var{form}s are involved, the
-assignments take place in parallel rather than sequentially.
-Specifically, all subforms are evaluated from left to right, then
-all the assignments are done (in an undefined order).
address@hidden defspec
-
address@hidden incf place &optional x
-This macro increments the number stored in @var{place} by one, or
-by @var{x} if specified. The incremented value is returned. For
-example, @code{(incf i)} is equivalent to @code{(setq i (1+ i))}, and
address@hidden(incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x)
2))}.
-
-Once again, care is taken to preserve the ``apparent'' order of
-evaluation. For example,
-
address@hidden
-(incf (aref vec (incf i)))
address@hidden example
-
address@hidden
-appears to increment @code{i} once, then increment the element of
address@hidden addressed by @code{i}; this is indeed exactly what it
-does, which means the above form is @emph{not} equivalent to the
-``obvious'' expansion,
-
address@hidden
-(setf (aref vec (incf i)) (1+ (aref vec (incf i)))) ; Wrong!
address@hidden example
-
address@hidden
-but rather to something more like
-
address@hidden
-(let ((temp (incf i)))
- (setf (aref vec temp) (1+ (aref vec temp))))
address@hidden example
-
address@hidden
-Again, all of this is taken care of automatically by @code{incf} and
-the other generalized-variable macros.
-
-As a more Emacs-specific example of @code{incf}, the expression
address@hidden(incf (point) @var{n})} is essentially equivalent to
address@hidden(forward-char @var{n})}.
address@hidden defspec
-
address@hidden decf place &optional x
-This macro decrements the number stored in @var{place} by one, or
-by @var{x} if specified.
address@hidden defspec
-
address@hidden pop place
-This macro removes and returns the first element of the list stored
-in @var{place}. It is analogous to @code{(prog1 (car @var{place})
-(setf @var{place} (cdr @var{place})))}, except that it takes care
-to evaluate all subforms only once.
address@hidden defspec
-
address@hidden push x place
-This macro inserts @var{x} at the front of the list stored in
address@hidden It is analogous to @code{(setf @var{place} (cons
address@hidden @var{place}))}, except for evaluation of the subforms.
address@hidden defspec
-
address@hidden pushnew x place @t{&key :test :test-not :key}
-This macro inserts @var{x} at the front of the list stored in
address@hidden, but only if @var{x} was not @code{eql} to any
-existing element of the list. The optional keyword arguments
-are interpreted in the same way as for @code{adjoin}.
address@hidden as Sets}.
address@hidden defspec
-
address@hidden shiftf address@hidden newvalue
-This macro shifts the @var{place}s left by one, shifting in the
-value of @var{newvalue} (which may be any Lisp expression, not just
-a generalized variable), and returning the value shifted out of
-the first @var{place}. Thus, @code{(shiftf @var{a} @var{b} @var{c}
address@hidden)} is equivalent to
-
address@hidden
-(prog1
- @var{a}
- (psetf @var{a} @var{b}
- @var{b} @var{c}
- @var{c} @var{d}))
address@hidden example
-
address@hidden
-except that the subforms of @var{a}, @var{b}, and @var{c} are actually
-evaluated only once each and in the apparent order.
address@hidden defspec
-
address@hidden rotatef address@hidden
-This macro rotates the @var{place}s left by one in circular fashion.
-Thus, @code{(rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
-
address@hidden
-(psetf @var{a} @var{b}
- @var{b} @var{c}
- @var{c} @var{d}
- @var{d} @var{a})
address@hidden example
-
address@hidden
-except for the evaluation of subforms. @code{rotatef} always
-returns @code{nil}. Note that @code{(rotatef @var{a} @var{b})}
-conveniently exchanges @var{a} and @var{b}.
address@hidden defspec
-
-The following macros were invented for this package; they have no
-analogues in Common Lisp.
-
address@hidden letf (address@hidden) address@hidden
-This macro is analogous to @code{let}, but for generalized variables
-rather than just symbols. Each @var{binding} should be of the form
address@hidden(@var{place} @var{value})}; the original contents of the
address@hidden are saved, the @var{value}s are stored in them, and
-then the body @var{form}s are executed. Afterwards, the @var{places}
-are set back to their original saved contents. This cleanup happens
-even if the @var{form}s exit irregularly due to a @code{throw} or an
-error.
-
-For example,
-
address@hidden
-(letf (((point) (point-min))
- (a 17))
- ...)
address@hidden example
-
address@hidden
-moves ``point'' in the current buffer to the beginning of the buffer,
-and also binds @code{a} to 17 (as if by a normal @code{let}, since
address@hidden is just a regular variable). After the body exits, @code{a}
-is set back to its original value and point is moved back to its
-original position.
-
-Note that @code{letf} on @code{(point)} is not quite like a
address@hidden, as the latter effectively saves a marker
-which tracks insertions and deletions in the buffer. Actually,
-a @code{letf} of @code{(point-marker)} is much closer to this
-behavior. (@code{point} and @code{point-marker} are equivalent
-as @code{setf} places; each will accept either an integer or a
-marker as the stored value.)
-
-Since generalized variables look like lists, @code{let}'s shorthand
-of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
-be ambiguous in @code{letf} and is not allowed.
-
-However, a @var{binding} specifier may be a one-element list
address@hidden(@var{place})}, which is similar to @samp{(@var{place}
address@hidden)}. In other words, the @var{place} is not disturbed
-on entry to the body, and the only effect of the @code{letf} is
-to restore the original value of @var{place} afterwards. (The
-redundant access-and-store suggested by the @code{(@var{place}
address@hidden)} example does not actually occur.)
-
-In most cases, the @var{place} must have a well-defined value on
-entry to the @code{letf} form. The only exceptions are plain
-variables and calls to @code{symbol-value} and @code{symbol-function}.
-If the symbol is not bound on entry, it is simply made unbound by
address@hidden or @code{fmakunbound} on exit.
address@hidden defspec
-
address@hidden letf* (address@hidden) address@hidden
-This macro is to @code{letf} what @code{let*} is to @code{let}:
-It does the bindings in sequential rather than parallel order.
address@hidden defspec
-
address@hidden callf @var{function} @var{place} @address@hidden
-This is the ``generic'' modify macro. It calls @var{function},
-which should be an unquoted function name, macro name, or lambda.
-It passes @var{place} and @var{args} as arguments, and assigns the
-result back to @var{place}. For example, @code{(incf @var{place}
address@hidden)} is the same as @code{(callf + @var{place} @var{n})}.
-Some more examples:
-
address@hidden
-(callf abs my-number)
-(callf concat (buffer-name) "<" (int-to-string n) ">")
-(callf union happy-people (list joe bob) :test 'same-person)
address@hidden example
-
address@hidden Setf}, for @code{define-modify-macro}, a way
-to create even more concise notations for modify macros. Note
-again that @code{callf} is an extension to standard Common Lisp.
address@hidden defspec
-
address@hidden callf2 @var{function} @var{arg1} @var{place} @address@hidden
-This macro is like @code{callf}, except that @var{place} is
-the @emph{second} argument of @var{function} rather than the
-first. For example, @code{(push @var{x} @var{place})} is
-equivalent to @code{(callf2 cons @var{x} @var{place})}.
address@hidden defspec
-
-The @code{callf} and @code{callf2} macros serve as building
-blocks for other macros like @code{incf}, @code{pushnew}, and
address@hidden The @code{letf} and @code{letf*}
-macros are used in the processing of symbol macros;
address@hidden Bindings}.
-
address@hidden Customizing Setf, , Modify Macros, Generalized Variables
address@hidden Customizing Setf
-
address@hidden
-Common Lisp defines three macros, @code{define-modify-macro},
address@hidden, and @code{define-setf-method}, that allow the
-user to extend generalized variables in various ways.
-
address@hidden define-modify-macro name arglist function [doc-string]
-This macro defines a ``read-modify-write'' macro similar to
address@hidden and @code{decf}. The macro @var{name} is defined
-to take a @var{place} argument followed by additional arguments
-described by @var{arglist}. The call
-
address@hidden
-(@var{name} @var{place} @var{args}...)
address@hidden example
-
address@hidden
-will be expanded to
-
address@hidden
-(callf @var{func} @var{place} @var{args}...)
address@hidden example
-
address@hidden
-which in turn is roughly equivalent to
-
address@hidden
-(setf @var{place} (@var{func} @var{place} @var{args}...))
address@hidden example
-
-For example:
-
address@hidden
-(define-modify-macro incf (&optional (n 1)) +)
-(define-modify-macro concatf (&rest args) concat)
address@hidden example
-
-Note that @code{&key} is not allowed in @var{arglist}, but
address@hidden&rest} is sufficient to pass keywords on to the function.
-
-Most of the modify macros defined by Common Lisp do not exactly
-follow the pattern of @code{define-modify-macro}. For example,
address@hidden takes its arguments in the wrong order, and @code{pop}
-is completely irregular. You can define these macros ``by hand''
-using @code{get-setf-method}, or consult the source file
address@hidden to see how to use the internal @code{setf}
-building blocks.
address@hidden defspec
-
address@hidden defsetf access-fn update-fn
-This is the simpler of two @code{defsetf} forms. Where
address@hidden is the name of a function which accesses a place,
-this declares @var{update-fn} to be the corresponding store
-function. From now on,
-
address@hidden
-(setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
address@hidden example
-
address@hidden
-will be expanded to
-
address@hidden
-(@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
address@hidden example
-
address@hidden
-The @var{update-fn} is required to be either a true function, or
-a macro which evaluates its arguments in a function-like way. Also,
-the @var{update-fn} is expected to return @var{value} as its result.
-Otherwise, the above expansion would not obey the rules for the way
address@hidden is supposed to behave.
-
-As a special (non-Common-Lisp) extension, a third argument of @code{t}
-to @code{defsetf} says that the @code{update-fn}'s return value is
-not suitable, so that the above @code{setf} should be expanded to
-something more like
-
address@hidden
-(let ((temp @var{value}))
- (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
- temp)
address@hidden example
-
-Some examples of the use of @code{defsetf}, drawn from the standard
-suite of setf methods, are:
-
address@hidden
-(defsetf car setcar)
-(defsetf symbol-value set)
-(defsetf buffer-name rename-buffer t)
address@hidden example
address@hidden defspec
-
address@hidden defsetf access-fn arglist (store-var) address@hidden
-This is the second, more complex, form of @code{defsetf}. It is
-rather like @code{defmacro} except for the additional @var{store-var}
-argument. The @var{forms} should return a Lisp form which stores
-the value of @var{store-var} into the generalized variable formed
-by a call to @var{access-fn} with arguments described by @var{arglist}.
-The @var{forms} may begin with a string which documents the @code{setf}
-method (analogous to the doc string that appears at the front of a
-function).
-
-For example, the simple form of @code{defsetf} is shorthand for
-
address@hidden
-(defsetf @var{access-fn} (&rest args) (store)
- (append '(@var{update-fn}) args (list store)))
address@hidden example
-
-The Lisp form that is returned can access the arguments from
address@hidden and @var{store-var} in an unrestricted fashion;
-macros like @code{setf} and @code{incf} which invoke this
-setf-method will insert temporary variables as needed to make
-sure the apparent order of evaluation is preserved.
-
-Another example drawn from the standard package:
-
address@hidden
-(defsetf nth (n x) (store)
- (list 'setcar (list 'nthcdr n x) store))
address@hidden example
address@hidden defspec
-
address@hidden define-setf-method access-fn arglist address@hidden
-This is the most general way to create new place forms. When
-a @code{setf} to @var{access-fn} with arguments described by
address@hidden is expanded, the @var{forms} are evaluated and
-must return a list of five items:
-
address@hidden
address@hidden
-A list of @dfn{temporary variables}.
-
address@hidden
-A list of @dfn{value forms} corresponding to the temporary variables
-above. The temporary variables will be bound to these value forms
-as the first step of any operation on the generalized variable.
-
address@hidden
-A list of exactly one @dfn{store variable} (generally obtained
-from a call to @code{gensym}).
-
address@hidden
-A Lisp form which stores the contents of the store variable into
-the generalized variable, assuming the temporaries have been
-bound as described above.
-
address@hidden
-A Lisp form which accesses the contents of the generalized variable,
-assuming the temporaries have been bound.
address@hidden enumerate
-
-This is exactly like the Common Lisp macro of the same name,
-except that the method returns a list of five values rather
-than the five values themselves, since Emacs Lisp does not
-support Common Lisp's notion of multiple return values.
-
-Once again, the @var{forms} may begin with a documentation string.
-
-A setf-method should be maximally conservative with regard to
-temporary variables. In the setf-methods generated by
address@hidden, the second return value is simply the list of
-arguments in the place form, and the first return value is a
-list of a corresponding number of temporary variables generated
-by @code{gensym}. Macros like @code{setf} and @code{incf} which
-use this setf-method will optimize away most temporaries that
-turn out to be unnecessary, so there is little reason for the
-setf-method itself to optimize.
address@hidden defspec
-
address@hidden get-setf-method place &optional env
-This function returns the setf-method for @var{place}, by
-invoking the definition previously recorded by @code{defsetf}
-or @code{define-setf-method}. The result is a list of five
-values as described above. You can use this function to build
-your own @code{incf}-like modify macros. (Actually, it is
-better to use the internal functions @code{cl-setf-do-modify}
-and @code{cl-setf-do-store}, which are a bit easier to use and
-which also do a number of optimizations; consult the source
-code for the @code{incf} function for a simple example.)
-
-The argument @var{env} specifies the ``environment'' to be
-passed on to @code{macroexpand} if @code{get-setf-method} should
-need to expand a macro in @var{place}. It should come from
-an @code{&environment} argument to the macro or setf-method
-that called @code{get-setf-method}.
-
-See also the source code for the setf-methods for @code{apply}
-and @code{substring}, each of which works by calling
address@hidden on a simpler case, then massaging
-the result in various ways.
address@hidden defun
-
-Modern Common Lisp defines a second, independent way to specify
-the @code{setf} behavior of a function, namely address@hidden
-functions'' whose names are lists @code{(setf @var{name})}
-rather than symbols. For example, @code{(defun (setf foo) @dots{})}
-defines the function that is used when @code{setf} is applied to
address@hidden This package does not currently support @code{setf}
-functions. In particular, it is a compile-time error to use
address@hidden on a form which has not already been @code{defsetf}'d
-or otherwise declared; in newer Common Lisps, this would not be
-an error since the function @code{(setf @var{func})} might be
-defined later.
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Variable Bindings, Conditionals, Generalized Variables, Control
Structure
address@hidden Variable Bindings
-
address@hidden
-These Lisp forms make bindings to variables and function names,
-analogous to Lisp's built-in @code{let} form.
-
address@hidden Macros}, for the @code{letf} and @code{letf*} forms which
-are also related to variable bindings.
-
address@hidden
-* Dynamic Bindings:: The `progv' form
-* Lexical Bindings:: `lexical-let' and lexical closures
-* Function Bindings:: `flet' and `labels'
-* Macro Bindings:: `macrolet' and `symbol-macrolet'
address@hidden menu
-
address@hidden Dynamic Bindings, Lexical Bindings, Variable Bindings, Variable
Bindings
address@hidden Dynamic Bindings
-
address@hidden
-The standard @code{let} form binds variables whose names are known
-at compile-time. The @code{progv} form provides an easy way to
-bind variables whose names are computed at run-time.
-
address@hidden progv symbols values address@hidden
-This form establishes @code{let}-style variable bindings on a
-set of variables computed at run-time. The expressions
address@hidden and @var{values} are evaluated, and must return lists
-of symbols and values, respectively. The symbols are bound to the
-corresponding values for the duration of the body @var{form}s.
-If @var{values} is shorter than @var{symbols}, the last few symbols
-are made unbound (as if by @code{makunbound}) inside the body.
-If @var{symbols} is shorter than @var{values}, the excess values
-are ignored.
address@hidden defspec
-
address@hidden Lexical Bindings, Function Bindings, Dynamic Bindings, Variable
Bindings
address@hidden Lexical Bindings
-
address@hidden
-The @dfn{CL} package defines the following macro which
-more closely follows the Common Lisp @code{let} form:
-
address@hidden lexical-let (address@hidden) address@hidden
-This form is exactly like @code{let} except that the bindings it
-establishes are purely lexical. Lexical bindings are similar to
-local variables in a language like C: Only the code physically
-within the body of the @code{lexical-let} (after macro expansion)
-may refer to the bound variables.
-
address@hidden
-(setq a 5)
-(defun foo (b) (+ a b))
-(let ((a 2)) (foo a))
- @result{} 4
-(lexical-let ((a 2)) (foo a))
- @result{} 7
address@hidden example
-
address@hidden
-In this example, a regular @code{let} binding of @code{a} actually
-makes a temporary change to the global variable @code{a}, so @code{foo}
-is able to see the binding of @code{a} to 2. But @code{lexical-let}
-actually creates a distinct local variable @code{a} for use within its
-body, without any effect on the global variable of the same name.
-
-The most important use of lexical bindings is to create @dfn{closures}.
-A closure is a function object that refers to an outside lexical
-variable. For example:
-
address@hidden
-(defun make-adder (n)
- (lexical-let ((n n))
- (function (lambda (m) (+ n m)))))
-(setq add17 (make-adder 17))
-(funcall add17 4)
- @result{} 21
address@hidden example
-
address@hidden
-The call @code{(make-adder 17)} returns a function object which adds
-17 to its argument. If @code{let} had been used instead of
address@hidden, the function object would have referred to the
-global @code{n}, which would have been bound to 17 only during the
-call to @code{make-adder} itself.
-
address@hidden
-(defun make-counter ()
- (lexical-let ((n 0))
- (function* (lambda (&optional (m 1)) (incf n m)))))
-(setq count-1 (make-counter))
-(funcall count-1 3)
- @result{} 3
-(funcall count-1 14)
- @result{} 17
-(setq count-2 (make-counter))
-(funcall count-2 5)
- @result{} 5
-(funcall count-1 2)
- @result{} 19
-(funcall count-2)
- @result{} 6
address@hidden example
-
address@hidden
-Here we see that each call to @code{make-counter} creates a distinct
-local variable @code{n}, which serves as a private counter for the
-function object that is returned.
-
-Closed-over lexical variables persist until the last reference to
-them goes away, just like all other Lisp objects. For example,
address@hidden refers to a function object which refers to an
-instance of the variable @code{n}; this is the only reference
-to that variable, so after @code{(setq count-2 nil)} the garbage
-collector would be able to delete this instance of @code{n}.
-Of course, if a @code{lexical-let} does not actually create any
-closures, then the lexical variables are free as soon as the
address@hidden returns.
-
-Many closures are used only during the extent of the bindings they
-refer to; these are known as ``downward funargs'' in Lisp parlance.
-When a closure is used in this way, regular Emacs Lisp dynamic
-bindings suffice and will be more efficient than @code{lexical-let}
-closures:
-
address@hidden
-(defun add-to-list (x list)
- (mapcar (lambda (y) (+ x y))) list)
-(add-to-list 7 '(1 2 5))
- @result{} (8 9 12)
address@hidden example
-
address@hidden
-Since this lambda is only used while @code{x} is still bound,
-it is not necessary to make a true closure out of it.
-
-You can use @code{defun} or @code{flet} inside a @code{lexical-let}
-to create a named closure. If several closures are created in the
-body of a single @code{lexical-let}, they all close over the same
-instance of the lexical variable.
-
-The @code{lexical-let} form is an extension to Common Lisp. In
-true Common Lisp, all bindings are lexical unless declared otherwise.
address@hidden defspec
-
address@hidden lexical-let* (address@hidden) address@hidden
-This form is just like @code{lexical-let}, except that the bindings
-are made sequentially in the manner of @code{let*}.
address@hidden defspec
-
address@hidden Function Bindings, Macro Bindings, Lexical Bindings, Variable
Bindings
address@hidden Function Bindings
-
address@hidden
-These forms make @code{let}-like bindings to functions instead
-of variables.
-
address@hidden flet (address@hidden) address@hidden
-This form establishes @code{let}-style bindings on the function
-cells of symbols rather than on the value cells. Each @var{binding}
-must be a list of the form @samp{(@var{name} @var{arglist}
address@hidden@dots{})}, which defines a function exactly as if
-it were a @code{defun*} form. The function @var{name} is defined
-accordingly for the duration of the body of the @code{flet}; then
-the old function definition, or lack thereof, is restored.
-
-While @code{flet} in Common Lisp establishes a lexical binding of
address@hidden, Emacs Lisp @code{flet} makes a dynamic binding. The
-result is that @code{flet} affects indirect calls to a function as
-well as calls directly inside the @code{flet} form itself.
-
-You can use @code{flet} to disable or modify the behavior of a
-function in a temporary fashion. This will even work on Emacs
-primitives, although note that some calls to primitive functions
-internal to Emacs are made without going through the symbol's
-function cell, and so will not be affected by @code{flet}. For
-example,
-
address@hidden
-(flet ((message (&rest args) (push args saved-msgs)))
- (do-something))
address@hidden example
-
-This code attempts to replace the built-in function @code{message}
-with a function that simply saves the messages in a list rather
-than displaying them. The original definition of @code{message}
-will be restored after @code{do-something} exits. This code will
-work fine on messages generated by other Lisp code, but messages
-generated directly inside Emacs will not be caught since they make
-direct C-language calls to the message routines rather than going
-through the Lisp @code{message} function.
-
-Functions defined by @code{flet} may use the full Common Lisp
-argument notation supported by @code{defun*}; also, the function
-body is enclosed in an implicit block as if by @code{defun*}.
address@hidden Structure}.
address@hidden defspec
-
address@hidden labels (address@hidden) address@hidden
-The @code{labels} form is like @code{flet}, except that it
-makes lexical bindings of the function names rather than
-dynamic bindings. (In true Common Lisp, both @code{flet} and
address@hidden make lexical bindings of slightly different sorts;
-since Emacs Lisp is dynamically bound by default, it seemed
-more appropriate for @code{flet} also to use dynamic binding.
-The @code{labels} form, with its lexical binding, is fully
-compatible with Common Lisp.)
-
-Lexical scoping means that all references to the named
-functions must appear physically within the body of the
address@hidden form. References may appear both in the body
address@hidden of @code{labels} itself, and in the bodies of
-the functions themselves. Thus, @code{labels} can define
-local recursive functions, or mutually-recursive sets of
-functions.
-
-A ``reference'' to a function name is either a call to that
-function, or a use of its name quoted by @code{quote} or
address@hidden to be passed on to, say, @code{mapcar}.
address@hidden defspec
-
address@hidden Macro Bindings, , Function Bindings, Variable Bindings
address@hidden Macro Bindings
-
address@hidden
-These forms create local macros and ``symbol macros.''
-
address@hidden macrolet (address@hidden) address@hidden
-This form is analogous to @code{flet}, but for macros instead of
-functions. Each @var{binding} is a list of the same form as the
-arguments to @code{defmacro*} (i.e., a macro name, argument list,
-and macro-expander forms). The macro is defined accordingly for
-use within the body of the @code{macrolet}.
-
-Because of the nature of macros, @code{macrolet} is lexically
-scoped even in Emacs Lisp: The @code{macrolet} binding will
-affect only calls that appear physically within the body
address@hidden, possibly after expansion of other macros in the
-body.
address@hidden defspec
-
address@hidden symbol-macrolet (address@hidden) address@hidden
-This form creates @dfn{symbol macros}, which are macros that look
-like variable references rather than function calls. Each
address@hidden is a list @samp{(@var{var} @var{expansion})};
-any reference to @var{var} within the body @var{forms} is
-replaced by @var{expansion}.
-
address@hidden
-(setq bar '(5 . 9))
-(symbol-macrolet ((foo (car bar)))
- (incf foo))
-bar
- @result{} (6 . 9)
address@hidden example
-
-A @code{setq} of a symbol macro is treated the same as a @code{setf}.
-I.e., @code{(setq foo 4)} in the above would be equivalent to
address@hidden(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
-
-Likewise, a @code{let} or @code{let*} binding a symbol macro is
-treated like a @code{letf} or @code{letf*}. This differs from true
-Common Lisp, where the rules of lexical scoping cause a @code{let}
-binding to shadow a @code{symbol-macrolet} binding. In this package,
-only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
-macro.
-
-There is no analogue of @code{defmacro} for symbol macros; all symbol
-macros are local. A typical use of @code{symbol-macrolet} is in the
-expansion of another macro:
-
address@hidden
-(defmacro* my-dolist ((x list) &rest body)
- (let ((var (gensym)))
- (list 'loop 'for var 'on list 'do
- (list* 'symbol-macrolet (list (list x (list 'car var)))
- body))))
-
-(setq mylist '(1 2 3 4))
-(my-dolist (x mylist) (incf x))
-mylist
- @result{} (2 3 4 5)
address@hidden example
-
address@hidden
-In this example, the @code{my-dolist} macro is similar to @code{dolist}
-(@pxref{Iteration}) except that the variable @code{x} becomes a true
-reference onto the elements of the list. The @code{my-dolist} call
-shown here expands to
-
address@hidden
-(loop for G1234 on mylist do
- (symbol-macrolet ((x (car G1234)))
- (incf x)))
address@hidden example
-
address@hidden
-which in turn expands to
-
address@hidden
-(loop for G1234 on mylist do (incf (car G1234)))
address@hidden example
-
address@hidden Facility}, for a description of the @code{loop} macro.
-This package defines a nonstandard @code{in-ref} loop clause that
-works much like @code{my-dolist}.
address@hidden defspec
-
address@hidden Conditionals, Blocks and Exits, Variable Bindings, Control
Structure
address@hidden Conditionals
-
address@hidden
-These conditional forms augment Emacs Lisp's simple @code{if},
address@hidden, @code{or}, and @code{cond} forms.
-
address@hidden case keyform address@hidden
-This macro evaluates @var{keyform}, then compares it with the key
-values listed in the various @var{clause}s. Whichever clause matches
-the key is executed; comparison is done by @code{eql}. If no clause
-matches, the @code{case} form returns @code{nil}. The clauses are
-of the form
-
address@hidden
-(@var{keylist} @address@hidden)
address@hidden example
-
address@hidden
-where @var{keylist} is a list of key values. If there is exactly
-one value, and it is not a cons cell or the symbol @code{nil} or
address@hidden, then it can be used by itself as a @var{keylist} without
-being enclosed in a list. All key values in the @code{case} form
-must be distinct. The final clauses may use @code{t} in place of
-a @var{keylist} to indicate a default clause that should be taken
-if none of the other clauses match. (The symbol @code{otherwise}
-is also recognized in place of @code{t}. To make a clause that
-matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
-enclose the symbol in a list.)
-
-For example, this expression reads a keystroke, then does one of
-four things depending on whether it is an @samp{a}, a @samp{b},
-a @key{RET} or @kbd{C-j}, or anything else.
-
address@hidden
-(case (read-char)
- (?a (do-a-thing))
- (?b (do-b-thing))
- ((?\r ?\n) (do-ret-thing))
- (t (do-other-thing)))
address@hidden example
address@hidden defspec
-
address@hidden ecase keyform address@hidden
-This macro is just like @code{case}, except that if the key does
-not match any of the clauses, an error is signaled rather than
-simply returning @code{nil}.
address@hidden defspec
-
address@hidden typecase keyform address@hidden
-This macro is a version of @code{case} that checks for types
-rather than values. Each @var{clause} is of the form
address@hidden(@var{type} @var{body}...)}. @xref{Type Predicates},
-for a description of type specifiers. For example,
-
address@hidden
-(typecase x
- (integer (munch-integer x))
- (float (munch-float x))
- (string (munch-integer (string-to-int x)))
- (t (munch-anything x)))
address@hidden example
-
-The type specifier @code{t} matches any type of object; the word
address@hidden is also allowed. To make one clause match any of
-several types, use an @code{(or ...)} type specifier.
address@hidden defspec
-
address@hidden etypecase keyform address@hidden
-This macro is just like @code{typecase}, except that if the key does
-not match any of the clauses, an error is signaled rather than
-simply returning @code{nil}.
address@hidden defspec
-
address@hidden Blocks and Exits, Iteration, Conditionals, Control Structure
address@hidden Blocks and Exits
-
address@hidden
-Common Lisp @dfn{blocks} provide a non-local exit mechanism very
-similar to @code{catch} and @code{throw}, but lexically rather than
-dynamically scoped. This package actually implements @code{block}
-in terms of @code{catch}; however, the lexical scoping allows the
-optimizing byte-compiler to omit the costly @code{catch} step if the
-body of the block does not actually @code{return-from} the block.
-
address@hidden block name address@hidden
-The @var{forms} are evaluated as if by a @code{progn}. However,
-if any of the @var{forms} execute @code{(return-from @var{name})},
-they will jump out and return directly from the @code{block} form.
-The @code{block} returns the result of the last @var{form} unless
-a @code{return-from} occurs.
-
-The @code{block}/@code{return-from} mechanism is quite similar to
-the @code{catch}/@code{throw} mechanism. The main differences are
-that block @var{name}s are unevaluated symbols, rather than forms
-(such as quoted symbols) which evaluate to a tag at run-time; and
-also that blocks are lexically scoped whereas @code{catch}/@code{throw}
-are dynamically scoped. This means that functions called from the
-body of a @code{catch} can also @code{throw} to the @code{catch},
-but the @code{return-from} referring to a block name must appear
-physically within the @var{forms} that make up the body of the block.
-They may not appear within other called functions, although they may
-appear within macro expansions or @code{lambda}s in the body. Block
-names and @code{catch} names form independent name-spaces.
-
-In true Common Lisp, @code{defun} and @code{defmacro} surround
-the function or expander bodies with implicit blocks with the
-same name as the function or macro. This does not occur in Emacs
-Lisp, but this package provides @code{defun*} and @code{defmacro*}
-forms which do create the implicit block.
-
-The Common Lisp looping constructs defined by this package,
-such as @code{loop} and @code{dolist}, also create implicit blocks
-just as in Common Lisp.
-
-Because they are implemented in terms of Emacs Lisp @code{catch}
-and @code{throw}, blocks have the same overhead as actual
address@hidden constructs (roughly two function calls). However,
-the optimizing byte compiler will optimize away the @code{catch}
-if the block does
-not in fact contain any @code{return} or @code{return-from} calls
-that jump to it. This means that @code{do} loops and @code{defun*}
-functions which don't use @code{return} don't pay the overhead to
-support it.
address@hidden defspec
-
address@hidden return-from name [result]
-This macro returns from the block named @var{name}, which must be
-an (unevaluated) symbol. If a @var{result} form is specified, it
-is evaluated to produce the result returned from the @code{block}.
-Otherwise, @code{nil} is returned.
address@hidden defspec
-
address@hidden return [result]
-This macro is exactly like @code{(return-from nil @var{result})}.
-Common Lisp loops like @code{do} and @code{dolist} implicitly enclose
-themselves in @code{nil} blocks.
address@hidden defspec
-
address@hidden Iteration, Loop Facility, Blocks and Exits, Control Structure
address@hidden Iteration
-
address@hidden
-The macros described here provide more sophisticated, high-level
-looping constructs to complement Emacs Lisp's basic @code{while}
-loop.
-
address@hidden loop address@hidden
-The @dfn{CL} package supports both the simple, old-style meaning of
address@hidden and the extremely powerful and flexible feature known as
-the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
-facility is discussed in the following section; @pxref{Loop Facility}.
-The simple form of @code{loop} is described here.
-
-If @code{loop} is followed by zero or more Lisp expressions,
-then @code{(loop @address@hidden)} simply creates an infinite
-loop executing the expressions over and over. The loop is
-enclosed in an implicit @code{nil} block. Thus,
-
address@hidden
-(loop (foo) (if (no-more) (return 72)) (bar))
address@hidden example
-
address@hidden
-is exactly equivalent to
-
address@hidden
-(block nil (while t (foo) (if (no-more) (return 72)) (bar)))
address@hidden example
-
-If any of the expressions are plain symbols, the loop is instead
-interpreted as a Loop Macro specification as described later.
-(This is not a restriction in practice, since a plain symbol
-in the above notation would simply access and throw away the
-value of a variable.)
address@hidden defspec
-
address@hidden do (address@hidden) (end-test address@hidden) address@hidden
-This macro creates a general iterative loop. Each @var{spec} is
-of the form
-
address@hidden
-(@var{var} address@hidden address@hidden)
address@hidden example
-
-The loop works as follows: First, each @var{var} is bound to the
-associated @var{init} value as if by a @code{let} form. Then, in
-each iteration of the loop, the @var{end-test} is evaluated; if
-true, the loop is finished. Otherwise, the body @var{forms} are
-evaluated, then each @var{var} is set to the associated @var{step}
-expression (as if by a @code{psetq} form) and the next iteration
-begins. Once the @var{end-test} becomes true, the @var{result}
-forms are evaluated (with the @var{var}s still bound to their
-values) to produce the result returned by @code{do}.
-
-The entire @code{do} loop is enclosed in an implicit @code{nil}
-block, so that you can use @code{(return)} to break out of the
-loop at any time.
-
-If there are no @var{result} forms, the loop returns @code{nil}.
-If a given @var{var} has no @var{step} form, it is bound to its
address@hidden value but not otherwise modified during the @code{do}
-loop (unless the code explicitly modifies it); this case is just
-a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
-around the loop. If @var{init} is also omitted it defaults to
address@hidden, and in this case a plain @address@hidden can be used
-in place of @samp{(@var{var})}, again following the analogy with
address@hidden
-
-This example (from Steele) illustrates a loop which applies the
-function @code{f} to successive pairs of values from the lists
address@hidden and @code{bar}; it is equivalent to the call
address@hidden(mapcar* 'f foo bar)}. Note that this loop has no body
address@hidden at all, performing all its work as side effects of
-the rest of the loop.
-
address@hidden
-(do ((x foo (cdr x))
- (y bar (cdr y))
- (z nil (cons (f (car x) (car y)) z)))
- ((or (null x) (null y))
- (nreverse z)))
address@hidden example
address@hidden defspec
-
address@hidden do* (address@hidden) (end-test address@hidden) address@hidden
-This is to @code{do} what @code{let*} is to @code{let}. In
-particular, the initial values are bound as if by @code{let*}
-rather than @code{let}, and the steps are assigned as if by
address@hidden rather than @code{psetq}.
-
-Here is another way to write the above loop:
-
address@hidden
-(do* ((xp foo (cdr xp))
- (yp bar (cdr yp))
- (x (car xp) (car xp))
- (y (car yp) (car yp))
- z)
- ((or (null xp) (null yp))
- (nreverse z))
- (push (f x y) z))
address@hidden example
address@hidden defspec
-
address@hidden dolist (var list [result]) address@hidden
-This is a more specialized loop which iterates across the elements
-of a list. @var{list} should evaluate to a list; the body @var{forms}
-are executed with @var{var} bound to each element of the list in
-turn. Finally, the @var{result} form (or @code{nil}) is evaluated
-with @var{var} bound to @code{nil} to produce the result returned by
-the loop. Unlike with Emacs's built in @code{dolist}, the loop is
-surrounded by an implicit @code{nil} block.
address@hidden defspec
-
address@hidden dotimes (var count [result]) address@hidden
-This is a more specialized loop which iterates a specified number
-of times. The body is executed with @var{var} bound to the integers
-from zero (inclusive) to @var{count} (exclusive), in turn. Then
-the @code{result} form is evaluated with @var{var} bound to the total
-number of iterations that were done (i.e., @code{(max 0 @var{count})})
-to get the return value for the loop form. Unlike with Emacs's built in
address@hidden, the loop is surrounded by an implicit @code{nil} block.
address@hidden defspec
-
address@hidden do-symbols (var [obarray [result]]) address@hidden
-This loop iterates over all interned symbols. If @var{obarray}
-is specified and is not @code{nil}, it loops over all symbols in
-that obarray. For each symbol, the body @var{forms} are evaluated
-with @var{var} bound to that symbol. The symbols are visited in
-an unspecified order. Afterward the @var{result} form, if any,
-is evaluated (with @var{var} bound to @code{nil}) to get the return
-value. The loop is surrounded by an implicit @code{nil} block.
address@hidden defspec
-
address@hidden do-all-symbols (var [result]) address@hidden
-This is identical to @code{do-symbols} except that the @var{obarray}
-argument is omitted; it always iterates over the default obarray.
address@hidden defspec
-
address@hidden over Sequences}, for some more functions for
-iterating over vectors or lists.
-
address@hidden Loop Facility, Multiple Values, Iteration, Control Structure
address@hidden Loop Facility
-
address@hidden
-A common complaint with Lisp's traditional looping constructs is
-that they are either too simple and limited, such as Common Lisp's
address@hidden or Emacs Lisp's @code{while}, or too unreadable and
-obscure, like Common Lisp's @code{do} loop.
-
-To remedy this, recent versions of Common Lisp have added a new
-construct called the ``Loop Facility'' or address@hidden macro,''
-with an easy-to-use but very powerful and expressive syntax.
-
address@hidden
-* Loop Basics:: `loop' macro, basic clause structure
-* Loop Examples:: Working examples of `loop' macro
-* For Clauses:: Clauses introduced by `for' or `as'
-* Iteration Clauses:: `repeat', `while', `thereis', etc.
-* Accumulation Clauses:: `collect', `sum', `maximize', etc.
-* Other Clauses:: `with', `if', `initially', `finally'
address@hidden menu
-
address@hidden Loop Basics, Loop Examples, Loop Facility, Loop Facility
address@hidden Loop Basics
-
address@hidden
-The @code{loop} macro essentially creates a mini-language within
-Lisp that is specially tailored for describing loops. While this
-language is a little strange-looking by the standards of regular Lisp,
-it turns out to be very easy to learn and well-suited to its purpose.
-
-Since @code{loop} is a macro, all parsing of the loop language
-takes place at byte-compile time; compiled @code{loop}s are just
-as efficient as the equivalent @code{while} loops written longhand.
-
address@hidden loop address@hidden
-A loop construct consists of a series of @var{clause}s, each
-introduced by a symbol like @code{for} or @code{do}. Clauses
-are simply strung together in the argument list of @code{loop},
-with minimal extra parentheses. The various types of clauses
-specify initializations, such as the binding of temporary
-variables, actions to be taken in the loop, stepping actions,
-and final cleanup.
-
-Common Lisp specifies a certain general order of clauses in a
-loop:
-
address@hidden
-(loop @var{name-clause}
- @address@hidden
- @address@hidden)
address@hidden example
-
-The @var{name-clause} optionally gives a name to the implicit
-block that surrounds the loop. By default, the implicit block
-is named @code{nil}. The @var{var-clauses} specify what
-variables should be bound during the loop, and how they should
-be modified or iterated throughout the course of the loop. The
address@hidden are things to be done during the loop, such
-as computing, collecting, and returning values.
-
-The Emacs version of the @code{loop} macro is less restrictive about
-the order of clauses, but things will behave most predictably if
-you put the variable-binding clauses @code{with}, @code{for}, and
address@hidden before the action clauses. As in Common Lisp,
address@hidden and @code{finally} clauses can go anywhere.
-
-Loops generally return @code{nil} by default, but you can cause
-them to return a value by using an accumulation clause like
address@hidden, an end-test clause like @code{always}, or an
-explicit @code{return} clause to jump out of the implicit block.
-(Because the loop body is enclosed in an implicit block, you can
-also use regular Lisp @code{return} or @code{return-from} to
-break out of the loop.)
address@hidden defspec
-
-The following sections give some examples of the Loop Macro in
-action, and describe the particular loop clauses in great detail.
-Consult the second edition of Steele's @dfn{Common Lisp, the Language},
-for additional discussion and examples of the @code{loop} macro.
-
address@hidden Loop Examples, For Clauses, Loop Basics, Loop Facility
address@hidden Loop Examples
-
address@hidden
-Before listing the full set of clauses that are allowed, let's
-look at a few example loops just to get a feel for the @code{loop}
-language.
-
address@hidden
-(loop for buf in (buffer-list)
- collect (buffer-file-name buf))
address@hidden example
-
address@hidden
-This loop iterates over all Emacs buffers, using the list
-returned by @code{buffer-list}. For each buffer @code{buf},
-it calls @code{buffer-file-name} and collects the results into
-a list, which is then returned from the @code{loop} construct.
-The result is a list of the file names of all the buffers in
-Emacs' memory. The words @code{for}, @code{in}, and @code{collect}
-are reserved words in the @code{loop} language.
-
address@hidden
-(loop repeat 20 do (insert "Yowsa\n"))
address@hidden example
-
address@hidden
-This loop inserts the phrase ``Yowsa'' twenty times in the
-current buffer.
-
address@hidden
-(loop until (eobp) do (munch-line) (forward-line 1))
address@hidden example
-
address@hidden
-This loop calls @code{munch-line} on every line until the end
-of the buffer. If point is already at the end of the buffer,
-the loop exits immediately.
-
address@hidden
-(loop do (munch-line) until (eobp) do (forward-line 1))
address@hidden example
-
address@hidden
-This loop is similar to the above one, except that @code{munch-line}
-is always called at least once.
-
address@hidden
-(loop for x from 1 to 100
- for y = (* x x)
- until (>= y 729)
- finally return (list x (= y 729)))
address@hidden example
-
address@hidden
-This more complicated loop searches for a number @code{x} whose
-square is 729. For safety's sake it only examines @code{x}
-values up to 100; dropping the phrase @samp{to 100} would
-cause the loop to count upwards with no limit. The second
address@hidden clause defines @code{y} to be the square of @code{x}
-within the loop; the expression after the @code{=} sign is
-reevaluated each time through the loop. The @code{until}
-clause gives a condition for terminating the loop, and the
address@hidden clause says what to do when the loop finishes.
-(This particular example was written less concisely than it
-could have been, just for the sake of illustration.)
-
-Note that even though this loop contains three clauses (two
address@hidden and an @code{until}) that would have been enough to
-define loops all by themselves, it still creates a single loop
-rather than some sort of triple-nested loop. You must explicitly
-nest your @code{loop} constructs if you want nested loops.
-
address@hidden For Clauses, Iteration Clauses, Loop Examples, Loop Facility
address@hidden For Clauses
-
address@hidden
-Most loops are governed by one or more @code{for} clauses.
-A @code{for} clause simultaneously describes variables to be
-bound, how those variables are to be stepped during the loop,
-and usually an end condition based on those variables.
-
-The word @code{as} is a synonym for the word @code{for}. This
-word is followed by a variable name, then a word like @code{from}
-or @code{across} that describes the kind of iteration desired.
-In Common Lisp, the phrase @code{being the} sometimes precedes
-the type of iteration; in this package both @code{being} and
address@hidden are optional. The word @code{each} is a synonym
-for @code{the}, and the word that follows it may be singular
-or plural: @samp{for x being the elements of y} or
address@hidden x being each element of y}. Which form you use
-is purely a matter of style.
-
-The variable is bound around the loop as if by @code{let}:
-
address@hidden
-(setq i 'happy)
-(loop for i from 1 to 10 do (do-something-with i))
-i
- @result{} happy
address@hidden example
-
address@hidden @code
address@hidden for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
-This type of @code{for} clause creates a counting loop. Each of
-the three sub-terms is optional, though there must be at least one
-term so that the clause is marked as a counting clause.
-
-The three expressions are the starting value, the ending value, and
-the step value, respectively, of the variable. The loop counts
-upwards by default (@var{expr3} must be positive), from @var{expr1}
-to @var{expr2} inclusively. If you omit the @code{from} term, the
-loop counts from zero; if you omit the @code{to} term, the loop
-counts forever without stopping (unless stopped by some other
-loop clause, of course); if you omit the @code{by} term, the loop
-counts in steps of one.
-
-You can replace the word @code{from} with @code{upfrom} or
address@hidden to indicate the direction of the loop. Likewise,
-you can replace @code{to} with @code{upto} or @code{downto}.
-For example, @samp{for x from 5 downto 1} executes five times
-with @code{x} taking on the integers from 5 down to 1 in turn.
-Also, you can replace @code{to} with @code{below} or @code{above},
-which are like @code{upto} and @code{downto} respectively except
-that they are exclusive rather than inclusive limits:
-
address@hidden
-(loop for x to 10 collect x)
- @result{} (0 1 2 3 4 5 6 7 8 9 10)
-(loop for x below 10 collect x)
- @result{} (0 1 2 3 4 5 6 7 8 9)
address@hidden example
-
-The @code{by} value is always positive, even for downward-counting
-loops. Some sort of @code{from} value is required for downward
-loops; @samp{for x downto 5} is not a valid loop clause all by
-itself.
-
address@hidden for @var{var} in @var{list} by @var{function}
-This clause iterates @var{var} over all the elements of @var{list},
-in turn. If you specify the @code{by} term, then @var{function}
-is used to traverse the list instead of @code{cdr}; it must be a
-function taking one argument. For example:
-
address@hidden
-(loop for x in '(1 2 3 4 5 6) collect (* x x))
- @result{} (1 4 9 16 25 36)
-(loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
- @result{} (1 9 25)
address@hidden example
-
address@hidden for @var{var} on @var{list} by @var{function}
-This clause iterates @var{var} over all the cons cells of @var{list}.
-
address@hidden
-(loop for x on '(1 2 3 4) collect x)
- @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
address@hidden example
-
-With @code{by}, there is no real reason that the @code{on} expression
-must be a list. For example:
-
address@hidden
-(loop for x on first-animal by 'next-animal collect x)
address@hidden example
-
address@hidden
-where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
-the next in the (assumed) sequence of animals, or @code{nil} if
address@hidden was the last animal in the sequence.
-
address@hidden for @var{var} in-ref @var{list} by @var{function}
-This is like a regular @code{in} clause, but @var{var} becomes
-a @code{setf}-able ``reference'' onto the elements of the list
-rather than just a temporary variable. For example,
-
address@hidden
-(loop for x in-ref my-list do (incf x))
address@hidden example
-
address@hidden
-increments every element of @code{my-list} in place. This clause
-is an extension to standard Common Lisp.
-
address@hidden for @var{var} across @var{array}
-This clause iterates @var{var} over all the elements of @var{array},
-which may be a vector or a string.
-
address@hidden
-(loop for x across "aeiou"
- do (use-vowel (char-to-string x)))
address@hidden example
-
address@hidden for @var{var} across-ref @var{array}
-This clause iterates over an array, with @var{var} a @code{setf}-able
-reference onto the elements; see @code{in-ref} above.
-
address@hidden for @var{var} being the elements of @var{sequence}
-This clause iterates over the elements of @var{sequence}, which may
-be a list, vector, or string. Since the type must be determined
-at run-time, this is somewhat less efficient than @code{in} or
address@hidden The clause may be followed by the additional term
address@hidden (index @var{var2})} to cause @var{var2} to be bound to
-the successive indices (starting at 0) of the elements.
-
-This clause type is taken from older versions of the @code{loop} macro,
-and is not present in modern Common Lisp. The @samp{using (sequence ...)}
-term of the older macros is not supported.
-
address@hidden for @var{var} being the elements of-ref @var{sequence}
-This clause iterates over a sequence, with @var{var} a @code{setf}-able
-reference onto the elements; see @code{in-ref} above.
-
address@hidden for @var{var} being the symbols [of @var{obarray}]
-This clause iterates over symbols, either over all interned symbols
-or over all symbols in @var{obarray}. The loop is executed with
address@hidden bound to each symbol in turn. The symbols are visited in
-an unspecified order.
-
-As an example,
-
address@hidden
-(loop for sym being the symbols
- when (fboundp sym)
- when (string-match "^map" (symbol-name sym))
- collect sym)
address@hidden example
-
address@hidden
-returns a list of all the functions whose names begin with @samp{map}.
-
-The Common Lisp words @code{external-symbols} and @code{present-symbols}
-are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
-
-Due to a minor implementation restriction, it will not work to have
-more than one @code{for} clause iterating over symbols, hash tables,
-keymaps, overlays, or intervals in a given @code{loop}. Fortunately,
-it would rarely if ever be useful to do so. It @emph{is} valid to mix
-one of these types of clauses with other clauses like @code{for ... to}
-or @code{while}.
-
address@hidden for @var{var} being the hash-keys of @var{hash-table}
-This clause iterates over the entries in @var{hash-table}. For each
-hash table entry, @var{var} is bound to the entry's key. If you write
address@hidden hash-values} instead, @var{var} is bound to the values
-of the entries. The clause may be followed by the additional
-term @samp{using (hash-values @var{var2})} (where @code{hash-values}
-is the opposite word of the word following @code{the}) to cause
address@hidden and @var{var2} to be bound to the two parts of each
-hash table entry.
-
address@hidden for @var{var} being the key-codes of @var{keymap}
-This clause iterates over the entries in @var{keymap}.
-The iteration does not enter nested keymaps or inherited (parent) keymaps.
-You can use @samp{the key-bindings} to access the commands bound to
-the keys rather than the key codes, and you can add a @code{using}
-clause to access both the codes and the bindings together.
-
address@hidden for @var{var} being the key-seqs of @var{keymap}
-This clause iterates over all key sequences defined by @var{keymap}
-and its nested keymaps, where @var{var} takes on values which are
-vectors. The strings or vectors
-are reused for each iteration, so you must copy them if you wish to keep
-them permanently. You can add a @samp{using (key-bindings ...)}
-clause to get the command bindings as well.
-
address@hidden for @var{var} being the overlays [of @var{buffer}] @dots{}
-This clause iterates over the ``overlays'' of a buffer
-(the clause @code{extents} is synonymous
-with @code{overlays}). If the @code{of} term is omitted, the current
-buffer is used.
-This clause also accepts optional @samp{from @var{pos}} and
address@hidden @var{pos}} terms, limiting the clause to overlays which
-overlap the specified region.
-
address@hidden for @var{var} being the intervals [of @var{buffer}] @dots{}
-This clause iterates over all intervals of a buffer with constant
-text properties. The variable @var{var} will be bound to conses
-of start and end positions, where one start position is always equal
-to the previous end position. The clause allows @code{of},
address@hidden, @code{to}, and @code{property} terms, where the latter
-term restricts the search to just the specified property. The
address@hidden term may specify either a buffer or a string.
-
address@hidden for @var{var} being the frames
-This clause iterates over all frames, i.e., X window system windows
-open on Emacs files. The
-clause @code{screens} is a synonym for @code{frames}. The frames
-are visited in @code{next-frame} order starting from
address@hidden
-
address@hidden for @var{var} being the windows [of @var{frame}]
-This clause iterates over the windows (in the Emacs sense) of
-the current frame, or of the specified @var{frame}.
-
address@hidden for @var{var} being the buffers
-This clause iterates over all buffers in Emacs. It is equivalent
-to @samp{for @var{var} in (buffer-list)}.
-
address@hidden for @var{var} = @var{expr1} then @var{expr2}
-This clause does a general iteration. The first time through
-the loop, @var{var} will be bound to @var{expr1}. On the second
-and successive iterations it will be set by evaluating @var{expr2}
-(which may refer to the old value of @var{var}). For example,
-these two loops are effectively the same:
-
address@hidden
-(loop for x on my-list by 'cddr do ...)
-(loop for x = my-list then (cddr x) while x do ...)
address@hidden example
-
-Note that this type of @code{for} clause does not imply any sort
-of terminating condition; the above example combines it with a
address@hidden clause to tell when to end the loop.
-
-If you omit the @code{then} term, @var{expr1} is used both for
-the initial setting and for successive settings:
-
address@hidden
-(loop for x = (random) when (> x 0) return x)
address@hidden example
-
address@hidden
-This loop keeps taking random numbers from the @code{(random)}
-function until it gets a positive one, which it then returns.
address@hidden table
-
-If you include several @code{for} clauses in a row, they are
-treated sequentially (as if by @code{let*} and @code{setq}).
-You can instead use the word @code{and} to link the clauses,
-in which case they are processed in parallel (as if by @code{let}
-and @code{psetq}).
-
address@hidden
-(loop for x below 5 for y = nil then x collect (list x y))
- @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
-(loop for x below 5 and y = nil then x collect (list x y))
- @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
address@hidden example
-
address@hidden
-In the first loop, @code{y} is set based on the value of @code{x}
-that was just set by the previous clause; in the second loop,
address@hidden and @code{y} are set simultaneously so @code{y} is set
-based on the value of @code{x} left over from the previous time
-through the loop.
-
-Another feature of the @code{loop} macro is @dfn{destructuring},
-similar in concept to the destructuring provided by @code{defmacro}.
-The @var{var} part of any @code{for} clause can be given as a list
-of variables instead of a single variable. The values produced
-during loop execution must be lists; the values in the lists are
-stored in the corresponding variables.
-
address@hidden
-(loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
- @result{} (5 9 13)
address@hidden example
-
-In loop destructuring, if there are more values than variables
-the trailing values are ignored, and if there are more variables
-than values the trailing variables get the value @code{nil}.
-If @code{nil} is used as a variable name, the corresponding
-values are ignored. Destructuring may be nested, and dotted
-lists of variables like @code{(x . y)} are allowed.
-
address@hidden Iteration Clauses, Accumulation Clauses, For Clauses, Loop
Facility
address@hidden Iteration Clauses
-
address@hidden
-Aside from @code{for} clauses, there are several other loop clauses
-that control the way the loop operates. They might be used by
-themselves, or in conjunction with one or more @code{for} clauses.
-
address@hidden @code
address@hidden repeat @var{integer}
-This clause simply counts up to the specified number using an
-internal temporary variable. The loops
-
address@hidden
-(loop repeat n do ...)
-(loop for temp to n do ...)
address@hidden example
-
address@hidden
-are identical except that the second one forces you to choose
-a name for a variable you aren't actually going to use.
-
address@hidden while @var{condition}
-This clause stops the loop when the specified condition (any Lisp
-expression) becomes @code{nil}. For example, the following two
-loops are equivalent, except for the implicit @code{nil} block
-that surrounds the second one:
-
address@hidden
-(while @var{cond} @address@hidden)
-(loop while @var{cond} do @address@hidden)
address@hidden example
-
address@hidden until @var{condition}
-This clause stops the loop when the specified condition is true,
-i.e., address@hidden
-
address@hidden always @var{condition}
-This clause stops the loop when the specified condition is @code{nil}.
-Unlike @code{while}, it stops the loop using @code{return nil} so that
-the @code{finally} clauses are not executed. If all the conditions
-were address@hidden, the loop returns @code{t}:
-
address@hidden
-(if (loop for size in size-list always (> size 10))
- (some-big-sizes)
- (no-big-sizes))
address@hidden example
-
address@hidden never @var{condition}
-This clause is like @code{always}, except that the loop returns
address@hidden if any conditions were false, or @code{nil} otherwise.
-
address@hidden thereis @var{condition}
-This clause stops the loop when the specified form is address@hidden;
-in this case, it returns that address@hidden value. If all the
-values were @code{nil}, the loop returns @code{nil}.
address@hidden table
-
address@hidden Accumulation Clauses, Other Clauses, Iteration Clauses, Loop
Facility
address@hidden Accumulation Clauses
-
address@hidden
-These clauses cause the loop to accumulate information about the
-specified Lisp @var{form}. The accumulated result is returned
-from the loop unless overridden, say, by a @code{return} clause.
-
address@hidden @code
address@hidden collect @var{form}
-This clause collects the values of @var{form} into a list. Several
-examples of @code{collect} appear elsewhere in this manual.
-
-The word @code{collecting} is a synonym for @code{collect}, and
-likewise for the other accumulation clauses.
-
address@hidden append @var{form}
-This clause collects lists of values into a result list using
address@hidden
-
address@hidden nconc @var{form}
-This clause collects lists of values into a result list by
-destructively modifying the lists rather than copying them.
-
address@hidden concat @var{form}
-This clause concatenates the values of the specified @var{form}
-into a string. (It and the following clause are extensions to
-standard Common Lisp.)
-
address@hidden vconcat @var{form}
-This clause concatenates the values of the specified @var{form}
-into a vector.
-
address@hidden count @var{form}
-This clause counts the number of times the specified @var{form}
-evaluates to a address@hidden value.
-
address@hidden sum @var{form}
-This clause accumulates the sum of the values of the specified
address@hidden, which must evaluate to a number.
-
address@hidden maximize @var{form}
-This clause accumulates the maximum value of the specified @var{form},
-which must evaluate to a number. The return value is undefined if
address@hidden is executed zero times.
-
address@hidden minimize @var{form}
-This clause accumulates the minimum value of the specified @var{form}.
address@hidden table
-
-Accumulation clauses can be followed by @samp{into @var{var}} to
-cause the data to be collected into variable @var{var} (which is
-automatically @code{let}-bound during the loop) rather than an
-unnamed temporary variable. Also, @code{into} accumulations do
-not automatically imply a return value. The loop must use some
-explicit mechanism, such as @code{finally return}, to return
-the accumulated result.
-
-It is valid for several accumulation clauses of the same type to
-accumulate into the same place. From Steele:
-
address@hidden
-(loop for name in '(fred sue alice joe june)
- for kids in '((bob ken) () () (kris sunshine) ())
- collect name
- append kids)
- @result{} (fred bob ken sue alice joe kris sunshine june)
address@hidden example
-
address@hidden Other Clauses, , Accumulation Clauses, Loop Facility
address@hidden Other Clauses
-
address@hidden
-This section describes the remaining loop clauses.
-
address@hidden @code
address@hidden with @var{var} = @var{value}
-This clause binds a variable to a value around the loop, but
-otherwise leaves the variable alone during the loop. The following
-loops are basically equivalent:
-
address@hidden
-(loop with x = 17 do ...)
-(let ((x 17)) (loop do ...))
-(loop for x = 17 then x do ...)
address@hidden example
-
-Naturally, the variable @var{var} might be used for some purpose
-in the rest of the loop. For example:
-
address@hidden
-(loop for x in my-list with res = nil do (push x res)
- finally return res)
address@hidden example
-
-This loop inserts the elements of @code{my-list} at the front of
-a new list being accumulated in @code{res}, then returns the
-list @code{res} at the end of the loop. The effect is similar
-to that of a @code{collect} clause, but the list gets reversed
-by virtue of the fact that elements are being pushed onto the
-front of @code{res} rather than the end.
-
-If you omit the @code{=} term, the variable is initialized to
address@hidden (Thus the @samp{= nil} in the above example is
-unnecessary.)
-
-Bindings made by @code{with} are sequential by default, as if
-by @code{let*}. Just like @code{for} clauses, @code{with} clauses
-can be linked with @code{and} to cause the bindings to be made by
address@hidden instead.
-
address@hidden if @var{condition} @var{clause}
-This clause executes the following loop clause only if the specified
-condition is true. The following @var{clause} should be an accumulation,
address@hidden, @code{return}, @code{if}, or @code{unless} clause.
-Several clauses may be linked by separating them with @code{and}.
-These clauses may be followed by @code{else} and a clause or clauses
-to execute if the condition was false. The whole construct may
-optionally be followed by the word @code{end} (which may be used to
-disambiguate an @code{else} or @code{and} in a nested @code{if}).
-
-The actual address@hidden value of the condition form is available
-by the name @code{it} in the ``then'' part. For example:
-
address@hidden
-(setq funny-numbers '(6 13 -1))
- @result{} (6 13 -1)
-(loop for x below 10
- if (oddp x)
- collect x into odds
- and if (memq x funny-numbers) return (cdr it) end
- else
- collect x into evens
- finally return (vector odds evens))
- @result{} [(1 3 5 7 9) (0 2 4 6 8)]
-(setq funny-numbers '(6 7 13 -1))
- @result{} (6 7 13 -1)
-(loop <@r{same thing again}>)
- @result{} (13 -1)
address@hidden example
-
-Note the use of @code{and} to put two clauses into the ``then''
-part, one of which is itself an @code{if} clause. Note also that
address@hidden, while normally optional, was necessary here to make
-it clear that the @code{else} refers to the outermost @code{if}
-clause. In the first case, the loop returns a vector of lists
-of the odd and even values of @var{x}. In the second case, the
-odd number 7 is one of the @code{funny-numbers} so the loop
-returns early; the actual returned value is based on the result
-of the @code{memq} call.
-
address@hidden when @var{condition} @var{clause}
-This clause is just a synonym for @code{if}.
-
address@hidden unless @var{condition} @var{clause}
-The @code{unless} clause is just like @code{if} except that the
-sense of the condition is reversed.
-
address@hidden named @var{name}
-This clause gives a name other than @code{nil} to the implicit
-block surrounding the loop. The @var{name} is the symbol to be
-used as the block name.
-
address@hidden initially [do] @var{forms}...
-This keyword introduces one or more Lisp forms which will be
-executed before the loop itself begins (but after any variables
-requested by @code{for} or @code{with} have been bound to their
-initial values). @code{initially} clauses can appear anywhere;
-if there are several, they are executed in the order they appear
-in the loop. The keyword @code{do} is optional.
-
address@hidden finally [do] @var{forms}...
-This introduces Lisp forms which will be executed after the loop
-finishes (say, on request of a @code{for} or @code{while}).
address@hidden and @code{finally} clauses may appear anywhere
-in the loop construct, but they are executed (in the specified
-order) at the beginning or end, respectively, of the loop.
-
address@hidden finally return @var{form}
-This says that @var{form} should be executed after the loop
-is done to obtain a return value. (Without this, or some other
-clause like @code{collect} or @code{return}, the loop will simply
-return @code{nil}.) Variables bound by @code{for}, @code{with},
-or @code{into} will still contain their final values when @var{form}
-is executed.
-
address@hidden do @var{forms}...
-The word @code{do} may be followed by any number of Lisp expressions
-which are executed as an implicit @code{progn} in the body of the
-loop. Many of the examples in this section illustrate the use of
address@hidden
-
address@hidden return @var{form}
-This clause causes the loop to return immediately. The following
-Lisp form is evaluated to give the return value of the @code{loop}
-form. The @code{finally} clauses, if any, are not executed.
-Of course, @code{return} is generally used inside an @code{if} or
address@hidden, as its use in a top-level loop clause would mean
-the loop would never get to ``loop'' more than once.
-
-The clause @samp{return @var{form}} is equivalent to
address@hidden (return @var{form})} (or @code{return-from} if the loop
-was named). The @code{return} clause is implemented a bit more
-efficiently, though.
address@hidden table
-
-While there is no high-level way to add user extensions to @code{loop}
-(comparable to @code{defsetf} for @code{setf}, say), this package
-does offer two properties called @code{cl-loop-handler} and
address@hidden which are functions to be called when
-a given symbol is encountered as a top-level loop clause or
address@hidden clause, respectively. Consult the source code in
-file @file{cl-macs.el} for details.
-
-This package's @code{loop} macro is compatible with that of Common
-Lisp, except that a few features are not implemented: @code{loop-finish}
-and data-type specifiers. Naturally, the @code{for} clauses which
-iterate over keymaps, overlays, intervals, frames, windows, and
-buffers are Emacs-specific extensions.
-
address@hidden Multiple Values, , Loop Facility, Control Structure
address@hidden Multiple Values
-
address@hidden
-Common Lisp functions can return zero or more results. Emacs Lisp
-functions, by contrast, always return exactly one result. This
-package makes no attempt to emulate Common Lisp multiple return
-values; Emacs versions of Common Lisp functions that return more
-than one value either return just the first value (as in
address@hidden) or return a list of values (as in
address@hidden). This package @emph{does} define placeholders
-for the Common Lisp functions that work with multiple values, but
-in Emacs Lisp these functions simply operate on lists instead.
-The @code{values} form, for example, is a synonym for @code{list}
-in Emacs.
-
address@hidden multiple-value-bind (address@hidden) values-form address@hidden
-This form evaluates @var{values-form}, which must return a list of
-values. It then binds the @var{var}s to these respective values,
-as if by @code{let}, and then executes the body @var{forms}.
-If there are more @var{var}s than values, the extra @var{var}s
-are bound to @code{nil}. If there are fewer @var{var}s than
-values, the excess values are ignored.
address@hidden defspec
-
address@hidden multiple-value-setq (address@hidden) form
-This form evaluates @var{form}, which must return a list of values.
-It then sets the @var{var}s to these respective values, as if by
address@hidden Extra @var{var}s or values are treated the same as
-in @code{multiple-value-bind}.
address@hidden defspec
-
-The older Quiroz package attempted a more faithful (but still
-imperfect) emulation of Common Lisp multiple values. The old
-method ``usually'' simulated true multiple values quite well,
-but under certain circumstances would leave spurious return
-values in memory where a later, unrelated @code{multiple-value-bind}
-form would see them.
-
-Since a perfect emulation is not feasible in Emacs Lisp, this
-package opts to keep it as simple and predictable as possible.
-
address@hidden Macros, Declarations, Control Structure, Top
address@hidden Macros
-
address@hidden
-This package implements the various Common Lisp features of
address@hidden, such as destructuring, @code{&environment},
-and @code{&body}. Top-level @code{&whole} is not implemented
-for @code{defmacro} due to technical difficulties.
address@hidden Lists}.
-
-Destructuring is made available to the user by way of the
-following macro:
-
address@hidden destructuring-bind arglist expr address@hidden
-This macro expands to code which executes @var{forms}, with
-the variables in @var{arglist} bound to the list of values
-returned by @var{expr}. The @var{arglist} can include all
-the features allowed for @code{defmacro} argument lists,
-including destructuring. (The @code{&environment} keyword
-is not allowed.) The macro expansion will signal an error
-if @var{expr} returns a list of the wrong number of arguments
-or with incorrect keyword arguments.
address@hidden defspec
-
-This package also includes the Common Lisp @code{define-compiler-macro}
-facility, which allows you to define compile-time expansions and
-optimizations for your functions.
-
address@hidden define-compiler-macro name arglist address@hidden
-This form is similar to @code{defmacro}, except that it only expands
-calls to @var{name} at compile-time; calls processed by the Lisp
-interpreter are not expanded, nor are they expanded by the
address@hidden function.
-
-The argument list may begin with a @code{&whole} keyword and a
-variable. This variable is bound to the macro-call form itself,
-i.e., to a list of the form @samp{(@var{name} @address@hidden)}.
-If the macro expander returns this form unchanged, then the
-compiler treats it as a normal function call. This allows
-compiler macros to work as optimizers for special cases of a
-function, leaving complicated cases alone.
-
-For example, here is a simplified version of a definition that
-appears as a standard part of this package:
-
address@hidden
-(define-compiler-macro member* (&whole form a list &rest keys)
- (if (and (null keys)
- (eq (car-safe a) 'quote)
- (not (floatp-safe (cadr a))))
- (list 'memq a list)
- form))
address@hidden example
-
address@hidden
-This definition causes @code{(member* @var{a} @var{list})} to change
-to a call to the faster @code{memq} in the common case where @var{a}
-is a non-floating-point constant; if @var{a} is anything else, or
-if there are any keyword arguments in the call, then the original
address@hidden call is left intact. (The actual compiler macro
-for @code{member*} optimizes a number of other cases, including
-common @code{:test} predicates.)
address@hidden defspec
-
address@hidden compiler-macroexpand form
-This function is analogous to @code{macroexpand}, except that it
-expands compiler macros rather than regular macros. It returns
address@hidden unchanged if it is not a call to a function for which
-a compiler macro has been defined, or if that compiler macro
-decided to punt by returning its @code{&whole} argument. Like
address@hidden, it expands repeatedly until it reaches a form
-for which no further expansion is possible.
address@hidden defun
-
address@hidden Bindings}, for descriptions of the @code{macrolet}
-and @code{symbol-macrolet} forms for making ``local'' macro
-definitions.
-
address@hidden Declarations, Symbols, Macros, Top
address@hidden Declarations
-
address@hidden
-Common Lisp includes a complex and powerful ``declaration''
-mechanism that allows you to give the compiler special hints
-about the types of data that will be stored in particular variables,
-and about the ways those variables and functions will be used. This
-package defines versions of all the Common Lisp declaration forms:
address@hidden, @code{locally}, @code{proclaim}, @code{declaim},
-and @code{the}.
-
-Most of the Common Lisp declarations are not currently useful in
-Emacs Lisp, as the byte-code system provides little opportunity
-to benefit from type information, and @code{special} declarations
-are redundant in a fully dynamically-scoped Lisp. A few
-declarations are meaningful when the optimizing byte
-compiler is being used, however. Under the earlier non-optimizing
-compiler, these declarations will effectively be ignored.
-
address@hidden proclaim decl-spec
-This function records a ``global'' declaration specified by
address@hidden Since @code{proclaim} is a function, @var{decl-spec}
-is evaluated and thus should normally be quoted.
address@hidden defun
-
address@hidden declaim address@hidden
-This macro is like @code{proclaim}, except that it takes any number
-of @var{decl-spec} arguments, and the arguments are unevaluated and
-unquoted. The @code{declaim} macro also puts an @code{(eval-when
-(compile load eval) ...)} around the declarations so that they will
-be registered at compile-time as well as at run-time. (This is vital,
-since normally the declarations are meant to influence the way the
-compiler treats the rest of the file that contains the @code{declaim}
-form.)
address@hidden defspec
-
address@hidden declare address@hidden
-This macro is used to make declarations within functions and other
-code. Common Lisp allows declarations in various locations, generally
-at the beginning of any of the many ``implicit @code{progn}s''
-throughout Lisp syntax, such as function bodies, @code{let} bodies,
-etc. Currently the only declaration understood by @code{declare}
-is @code{special}.
address@hidden defspec
-
address@hidden locally address@hidden address@hidden
-In this package, @code{locally} is no different from @code{progn}.
address@hidden defspec
-
address@hidden the type form
-Type information provided by @code{the} is ignored in this package;
-in other words, @code{(the @var{type} @var{form})} is equivalent
-to @var{form}. Future versions of the optimizing byte-compiler may
-make use of this information.
-
-For example, @code{mapcar} can map over both lists and arrays. It is
-hard for the compiler to expand @code{mapcar} into an in-line loop
-unless it knows whether the sequence will be a list or an array ahead
-of time. With @code{(mapcar 'car (the vector foo))}, a future
-compiler would have enough information to expand the loop in-line.
-For now, Emacs Lisp will treat the above code as exactly equivalent
-to @code{(mapcar 'car foo)}.
address@hidden defspec
-
-Each @var{decl-spec} in a @code{proclaim}, @code{declaim}, or
address@hidden should be a list beginning with a symbol that says
-what kind of declaration it is. This package currently understands
address@hidden, @code{inline}, @code{notinline}, @code{optimize},
-and @code{warn} declarations. (The @code{warn} declaration is an
-extension of standard Common Lisp.) Other Common Lisp declarations,
-such as @code{type} and @code{ftype}, are silently ignored.
-
address@hidden @code
address@hidden special
-Since all variables in Emacs Lisp are ``special'' (in the Common
-Lisp sense), @code{special} declarations are only advisory. They
-simply tell the optimizing byte compiler that the specified
-variables are intentionally being referred to without being
-bound in the body of the function. The compiler normally emits
-warnings for such references, since they could be typographical
-errors for references to local variables.
-
-The declaration @code{(declare (special @var{var1} @var{var2}))} is
-equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
-optimizing compiler, or to nothing at all in older compilers (which
-do not warn for non-local references).
-
-In top-level contexts, it is generally better to write
address@hidden(defvar @var{var})} than @code{(declaim (special @var{var}))},
-since @code{defvar} makes your intentions clearer. But the older
-byte compilers can not handle @code{defvar}s appearing inside of
-functions, while @code{(declare (special @var{var}))} takes care
-to work correctly with all compilers.
-
address@hidden inline
-The @code{inline} @var{decl-spec} lists one or more functions
-whose bodies should be expanded ``in-line'' into calling functions
-whenever the compiler is able to arrange for it. For example,
-the Common Lisp function @code{cadr} is declared @code{inline}
-by this package so that the form @code{(cadr @var{x})} will
-expand directly into @code{(car (cdr @var{x}))} when it is called
-in user functions, for a savings of one (relatively expensive)
-function call.
-
-The following declarations are all equivalent. Note that the
address@hidden form is a convenient way to define a function
-and declare it inline all at once.
-
address@hidden
-(declaim (inline foo bar))
-(eval-when (compile load eval) (proclaim '(inline foo bar)))
-(defsubst foo (...) ...) ; instead of defun
address@hidden example
-
address@hidden note:} this declaration remains in effect after the
-containing source file is done. It is correct to use it to
-request that a function you have defined should be inlined,
-but it is impolite to use it to request inlining of an external
-function.
-
-In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
-before a particular call to a function to cause just that call to
-be inlined; the current byte compilers provide no way to implement
-this, so @code{(declare (inline @dots{}))} is currently ignored by
-this package.
-
address@hidden notinline
-The @code{notinline} declaration lists functions which should
-not be inlined after all; it cancels a previous @code{inline}
-declaration.
-
address@hidden optimize
-This declaration controls how much optimization is performed by
-the compiler. Naturally, it is ignored by the earlier non-optimizing
-compilers.
-
-The word @code{optimize} is followed by any number of lists like
address@hidden(speed 3)} or @code{(safety 2)}. Common Lisp defines several
-optimization ``qualities''; this package ignores all but @code{speed}
-and @code{safety}. The value of a quality should be an integer from
-0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important.''
-The default level for both qualities is 1.
-
-In this package, with the optimizing compiler, the
address@hidden quality is tied to the @code{byte-compile-optimize}
-flag, which is set to @code{nil} for @code{(speed 0)} and to
address@hidden for higher settings; and the @code{safety} quality is
-tied to the @code{byte-compile-delete-errors} flag, which is
-set to @code{t} for @code{(safety 3)} and to @code{nil} for all
-lower settings. (The latter flag controls whether the compiler
-is allowed to optimize out code whose only side-effect could
-be to signal an error, e.g., rewriting @code{(progn foo bar)} to
address@hidden when it is not known whether @code{foo} will be bound
-at run-time.)
-
-Note that even compiling with @code{(safety 0)}, the Emacs
-byte-code system provides sufficient checking to prevent real
-harm from being done. For example, barring serious bugs in
-Emacs itself, Emacs will not crash with a segmentation fault
-just because of an error in a fully-optimized Lisp program.
-
-The @code{optimize} declaration is normally used in a top-level
address@hidden or @code{declaim} in a file; Common Lisp allows
-it to be used with @code{declare} to set the level of optimization
-locally for a given form, but this will not work correctly with the
-current version of the optimizing compiler. (The @code{declare}
-will set the new optimization level, but that level will not
-automatically be unset after the enclosing form is done.)
-
address@hidden warn
-This declaration controls what sorts of warnings are generated
-by the byte compiler. Again, only the optimizing compiler
-generates warnings. The word @code{warn} is followed by any
-number of ``warning qualities,'' similar in form to optimization
-qualities. The currently supported warning types are
address@hidden, @code{callargs}, @code{unresolved}, and
address@hidden; in the current system, a value of 0 will
-disable these warnings and any higher value will enable them.
-See the documentation for the optimizing byte compiler for details.
address@hidden table
-
address@hidden Symbols, Numbers, Declarations, Top
address@hidden Symbols
-
address@hidden
-This package defines several symbol-related features that were
-missing from Emacs Lisp.
-
address@hidden
-* Property Lists:: `get*', `remprop', `getf', `remf'
-* Creating Symbols:: `gensym', `gentemp'
address@hidden menu
-
address@hidden Property Lists, Creating Symbols, Symbols, Symbols
address@hidden Property Lists
-
address@hidden
-These functions augment the standard Emacs Lisp functions @code{get}
-and @code{put} for operating on properties attached to symbols.
-There are also functions for working with property lists as
-first-class data structures not attached to particular symbols.
-
address@hidden get* symbol property &optional default
-This function is like @code{get}, except that if the property is
-not found, the @var{default} argument provides the return value.
-(The Emacs Lisp @code{get} function always uses @code{nil} as
-the default; this package's @code{get*} is equivalent to Common
-Lisp's @code{get}.)
-
-The @code{get*} function is @code{setf}-able; when used in this
-fashion, the @var{default} argument is allowed but ignored.
address@hidden defun
-
address@hidden remprop symbol property
-This function removes the entry for @var{property} from the property
-list of @var{symbol}. It returns a true value if the property was
-indeed found and removed, or @code{nil} if there was no such property.
-(This function was probably omitted from Emacs originally because,
-since @code{get} did not allow a @var{default}, it was very difficult
-to distinguish between a missing property and a property whose value
-was @code{nil}; thus, setting a property to @code{nil} was close
-enough to @code{remprop} for most purposes.)
address@hidden defun
-
address@hidden getf place property &optional default
-This function scans the list @var{place} as if it were a property
-list, i.e., a list of alternating property names and values. If
-an even-numbered element of @var{place} is found which is @code{eq}
-to @var{property}, the following odd-numbered element is returned.
-Otherwise, @var{default} is returned (or @code{nil} if no default
-is given).
-
-In particular,
-
address@hidden
-(get sym prop) @equiv{} (getf (symbol-plist sym) prop)
address@hidden example
-
-It is valid to use @code{getf} as a @code{setf} place, in which case
-its @var{place} argument must itself be a valid @code{setf} place.
-The @var{default} argument, if any, is ignored in this context.
-The effect is to change (via @code{setcar}) the value cell in the
-list that corresponds to @var{property}, or to cons a new property-value
-pair onto the list if the property is not yet present.
-
address@hidden
-(put sym prop val) @equiv{} (setf (getf (symbol-plist sym) prop) val)
address@hidden example
-
-The @code{get} and @code{get*} functions are also @code{setf}-able.
-The fact that @code{default} is ignored can sometimes be useful:
-
address@hidden
-(incf (get* 'foo 'usage-count 0))
address@hidden example
-
-Here, symbol @code{foo}'s @code{usage-count} property is incremented
-if it exists, or set to 1 (an incremented 0) otherwise.
-
-When not used as a @code{setf} form, @code{getf} is just a regular
-function and its @var{place} argument can actually be any Lisp
-expression.
address@hidden defun
-
address@hidden remf place property
-This macro removes the property-value pair for @var{property} from
-the property list stored at @var{place}, which is any @code{setf}-able
-place expression. It returns true if the property was found. Note
-that if @var{property} happens to be first on the list, this will
-effectively do a @code{(setf @var{place} (cddr @var{place}))},
-whereas if it occurs later, this simply uses @code{setcdr} to splice
-out the property and value cells.
address@hidden defspec
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Creating Symbols, , Property Lists, Symbols
address@hidden Creating Symbols
-
address@hidden
-These functions create unique symbols, typically for use as
-temporary variables.
-
address@hidden gensym &optional x
-This function creates a new, uninterned symbol (using @code{make-symbol})
-with a unique name. (The name of an uninterned symbol is relevant
-only if the symbol is printed.) By default, the name is generated
-from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
address@hidden, etc. If the optional argument @var{x} is a string, that
-string is used as a prefix instead of @samp{G}. Uninterned symbols
-are used in macro expansions for temporary variables, to ensure that
-their names will not conflict with ``real'' variables in the user's
-code.
address@hidden defun
-
address@hidden *gensym-counter*
-This variable holds the counter used to generate @code{gensym} names.
-It is incremented after each use by @code{gensym}. In Common Lisp
-this is initialized with 0, but this package initializes it with a
-random (time-dependent) value to avoid trouble when two files that
-each used @code{gensym} in their compilation are loaded together.
-(Uninterned symbols become interned when the compiler writes them
-out to a file and the Emacs loader loads them, so their names have to
-be treated a bit more carefully than in Common Lisp where uninterned
-symbols remain uninterned after loading.)
address@hidden defvar
-
address@hidden gentemp &optional x
-This function is like @code{gensym}, except that it produces a new
address@hidden symbol. If the symbol that is generated already
-exists, the function keeps incrementing the counter and trying
-again until a new symbol is generated.
address@hidden defun
-
-The Quiroz @file{cl.el} package also defined a @code{defkeyword}
-form for creating self-quoting keyword symbols. This package
-automatically creates all keywords that are called for by
address@hidden&key} argument specifiers, and discourages the use of
-keywords as data unrelated to keyword arguments, so the
address@hidden form has been discontinued.
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Numbers, Sequences, Symbols, Top
address@hidden Numbers
-
address@hidden
-This section defines a few simple Common Lisp operations on numbers
-which were left out of Emacs Lisp.
-
address@hidden
-* Predicates on Numbers:: `plusp', `oddp', `floatp-safe', etc.
-* Numerical Functions:: `abs', `floor*', etc.
-* Random Numbers:: `random*', `make-random-state'
-* Implementation Parameters:: `most-positive-float'
address@hidden menu
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Predicates on Numbers, Numerical Functions, Numbers, Numbers
address@hidden Predicates on Numbers
-
address@hidden
-These functions return @code{t} if the specified condition is
-true of the numerical argument, or @code{nil} otherwise.
-
address@hidden plusp number
-This predicate tests whether @var{number} is positive. It is an
-error if the argument is not a number.
address@hidden defun
-
address@hidden minusp number
-This predicate tests whether @var{number} is negative. It is an
-error if the argument is not a number.
address@hidden defun
-
address@hidden oddp integer
-This predicate tests whether @var{integer} is odd. It is an
-error if the argument is not an integer.
address@hidden defun
-
address@hidden evenp integer
-This predicate tests whether @var{integer} is even. It is an
-error if the argument is not an integer.
address@hidden defun
-
address@hidden floatp-safe object
-This predicate tests whether @var{object} is a floating-point
-number. On systems that support floating-point, this is equivalent
-to @code{floatp}. On other systems, this always returns @code{nil}.
address@hidden defun
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Numerical Functions, Random Numbers, Predicates on Numbers,
Numbers
address@hidden Numerical Functions
-
address@hidden
-These functions perform various arithmetic operations on numbers.
-
address@hidden gcd &rest integers
-This function returns the Greatest Common Divisor of the arguments.
-For one argument, it returns the absolute value of that argument.
-For zero arguments, it returns zero.
address@hidden defun
-
address@hidden lcm &rest integers
-This function returns the Least Common Multiple of the arguments.
-For one argument, it returns the absolute value of that argument.
-For zero arguments, it returns one.
address@hidden defun
-
address@hidden isqrt integer
-This function computes the ``integer square root'' of its integer
-argument, i.e., the greatest integer less than or equal to the true
-square root of the argument.
address@hidden defun
-
address@hidden floor* number &optional divisor
-This function implements the Common Lisp @code{floor} function.
-It is called @code{floor*} to avoid name conflicts with the
-simpler @code{floor} function built-in to Emacs.
-
-With one argument, @code{floor*} returns a list of two numbers:
-The argument rounded down (toward minus infinity) to an integer,
-and the ``remainder'' which would have to be added back to the
-first return value to yield the argument again. If the argument
-is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
-If the argument is a floating-point number, the first
-result is a Lisp integer and the second is a Lisp float between
-0 (inclusive) and 1 (exclusive).
-
-With two arguments, @code{floor*} divides @var{number} by
address@hidden, and returns the floor of the quotient and the
-corresponding remainder as a list of two numbers. If
address@hidden(floor* @var{x} @var{y})} returns @code{(@var{q} @var{r})},
-then @address@hidden@var{y} + @var{r} = @var{x}}, with @var{r}
-between 0 (inclusive) and @var{r} (exclusive). Also, note
-that @code{(floor* @var{x})} is exactly equivalent to
address@hidden(floor* @var{x} 1)}.
-
-This function is entirely compatible with Common Lisp's @code{floor}
-function, except that it returns the two results in a list since
-Emacs Lisp does not support multiple-valued functions.
address@hidden defun
-
address@hidden ceiling* number &optional divisor
-This function implements the Common Lisp @code{ceiling} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments up toward plus infinity.
-The remainder will be between 0 and minus @var{r}.
address@hidden defun
-
address@hidden truncate* number &optional divisor
-This function implements the Common Lisp @code{truncate} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments toward zero. Thus it is
-equivalent to @code{floor*} if the argument or quotient is
-positive, or to @code{ceiling*} otherwise. The remainder has
-the same sign as @var{number}.
address@hidden defun
-
address@hidden round* number &optional divisor
-This function implements the Common Lisp @code{round} function,
-which is analogous to @code{floor} except that it rounds the
-argument or quotient of the arguments to the nearest integer.
-In the case of a tie (the argument or quotient is exactly
-halfway between two integers), it rounds to the even integer.
address@hidden defun
-
address@hidden mod* number divisor
-This function returns the same value as the second return value
-of @code{floor}.
address@hidden defun
-
address@hidden rem* number divisor
-This function returns the same value as the second return value
-of @code{truncate}.
address@hidden defun
-
-These definitions are compatible with those in the Quiroz
address@hidden package, except that this package appends @samp{*}
-to certain function names to avoid conflicts with existing
-Emacs functions, and that the mechanism for returning
-multiple values is different.
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Random Numbers, Implementation Parameters, Numerical Functions,
Numbers
address@hidden Random Numbers
-
address@hidden
-This package also provides an implementation of the Common Lisp
-random number generator. It uses its own additive-congruential
-algorithm, which is much more likely to give statistically clean
-random numbers than the simple generators supplied by many
-operating systems.
-
address@hidden random* number &optional state
-This function returns a random nonnegative number less than
address@hidden, and of the same type (either integer or floating-point).
-The @var{state} argument should be a @code{random-state} object
-which holds the state of the random number generator. The
-function modifies this state object as a side effect. If
address@hidden is omitted, it defaults to the variable
address@hidden, which contains a pre-initialized
address@hidden object.
address@hidden defun
-
address@hidden *random-state*
-This variable contains the system ``default'' @code{random-state}
-object, used for calls to @code{random*} that do not specify an
-alternative state object. Since any number of programs in the
-Emacs process may be accessing @code{*random-state*} in interleaved
-fashion, the sequence generated from this variable will be
-irreproducible for all intents and purposes.
address@hidden defvar
-
address@hidden make-random-state &optional state
-This function creates or copies a @code{random-state} object.
-If @var{state} is omitted or @code{nil}, it returns a new copy of
address@hidden This is a copy in the sense that future
-sequences of calls to @code{(random* @var{n})} and
address@hidden(random* @var{n} @var{s})} (where @var{s} is the new
-random-state object) will return identical sequences of random
-numbers.
-
-If @var{state} is a @code{random-state} object, this function
-returns a copy of that object. If @var{state} is @code{t}, this
-function returns a new @code{random-state} object seeded from the
-date and time. As an extension to Common Lisp, @var{state} may also
-be an integer in which case the new object is seeded from that
-integer; each different integer seed will result in a completely
-different sequence of random numbers.
-
-It is valid to print a @code{random-state} object to a buffer or
-file and later read it back with @code{read}. If a program wishes
-to use a sequence of pseudo-random numbers which can be reproduced
-later for debugging, it can call @code{(make-random-state t)} to
-get a new sequence, then print this sequence to a file. When the
-program is later rerun, it can read the original run's random-state
-from the file.
address@hidden defun
-
address@hidden random-state-p object
-This predicate returns @code{t} if @var{object} is a
address@hidden object, or @code{nil} otherwise.
address@hidden defun
-
address@hidden Implementation Parameters, , Random Numbers, Numbers
address@hidden Implementation Parameters
-
address@hidden
-This package defines several useful constants having to with numbers.
-
-The following parameters have to do with floating-point numbers.
-This package determines their values by exercising the computer's
-floating-point arithmetic in various ways. Because this operation
-might be slow, the code for initializing them is kept in a separate
-function that must be called before the parameters can be used.
-
address@hidden cl-float-limits
-This function makes sure that the Common Lisp floating-point parameters
-like @code{most-positive-float} have been initialized. Until it is
-called, these parameters will be @code{nil}. If this version of Emacs
-does not support floats, the parameters will remain @code{nil}. If the
-parameters have already been initialized, the function returns
-immediately.
-
-The algorithm makes assumptions that will be valid for most modern
-machines, but will fail if the machine's arithmetic is extremely
-unusual, e.g., decimal.
address@hidden defun
-
-Since true Common Lisp supports up to four different floating-point
-precisions, it has families of constants like
address@hidden, @code{most-positive-double-float},
address@hidden, and so on. Emacs has only one
-floating-point precision, so this package omits the precision word
-from the constants' names.
-
address@hidden most-positive-float
-This constant equals the largest value a Lisp float can hold.
-For those systems whose arithmetic supports infinities, this is
-the largest @emph{finite} value. For IEEE machines, the value
-is approximately @code{1.79e+308}.
address@hidden defvar
-
address@hidden most-negative-float
-This constant equals the most-negative value a Lisp float can hold.
-(It is assumed to be equal to @code{(- most-positive-float)}.)
address@hidden defvar
-
address@hidden least-positive-float
-This constant equals the smallest Lisp float value greater than zero.
-For IEEE machines, it is about @code{4.94e-324} if denormals are
-supported or @code{2.22e-308} if not.
address@hidden defvar
-
address@hidden least-positive-normalized-float
-This constant equals the smallest @emph{normalized} Lisp float greater
-than zero, i.e., the smallest value for which IEEE denormalization
-will not result in a loss of precision. For IEEE machines, this
-value is about @code{2.22e-308}. For machines that do not support
-the concept of denormalization and gradual underflow, this constant
-will always equal @code{least-positive-float}.
address@hidden defvar
-
address@hidden least-negative-float
-This constant is the negative counterpart of @code{least-positive-float}.
address@hidden defvar
-
address@hidden least-negative-normalized-float
-This constant is the negative counterpart of
address@hidden
address@hidden defvar
-
address@hidden float-epsilon
-This constant is the smallest positive Lisp float that can be added
-to 1.0 to produce a distinct value. Adding a smaller number to 1.0
-will yield 1.0 again due to roundoff. For IEEE machines, epsilon
-is about @code{2.22e-16}.
address@hidden defvar
-
address@hidden float-negative-epsilon
-This is the smallest positive value that can be subtracted from
-1.0 to produce a distinct value. For IEEE machines, it is about
address@hidden
address@hidden defvar
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Sequences, Lists, Numbers, Top
address@hidden Sequences
-
address@hidden
-Common Lisp defines a number of functions that operate on
address@hidden, which are either lists, strings, or vectors.
-Emacs Lisp includes a few of these, notably @code{elt} and
address@hidden; this package defines most of the rest.
-
address@hidden
-* Sequence Basics:: Arguments shared by all sequence functions
-* Mapping over Sequences:: `mapcar*', `mapcan', `map', `every', etc.
-* Sequence Functions:: `subseq', `remove*', `substitute', etc.
-* Searching Sequences:: `find', `position', `count', `search', etc.
-* Sorting Sequences:: `sort*', `stable-sort', `merge'
address@hidden menu
-
address@hidden Sequence Basics, Mapping over Sequences, Sequences, Sequences
address@hidden Sequence Basics
-
address@hidden
-Many of the sequence functions take keyword arguments; @pxref{Argument
-Lists}. All keyword arguments are optional and, if specified,
-may appear in any order.
-
-The @code{:key} argument should be passed either @code{nil}, or a
-function of one argument. This key function is used as a filter
-through which the elements of the sequence are seen; for example,
address@hidden(find x y :key 'car)} is similar to @code{(assoc* x y)}:
-It searches for an element of the list whose @code{car} equals
address@hidden, rather than for an element which equals @code{x} itself.
-If @code{:key} is omitted or @code{nil}, the filter is effectively
-the identity function.
-
-The @code{:test} and @code{:test-not} arguments should be either
address@hidden, or functions of two arguments. The test function is
-used to compare two sequence elements, or to compare a search value
-with sequence elements. (The two values are passed to the test
-function in the same order as the original sequence function
-arguments from which they are derived, or, if they both come from
-the same sequence, in the same order as they appear in that sequence.)
-The @code{:test} argument specifies a function which must return
-true (address@hidden) to indicate a match; instead, you may use
address@hidden:test-not} to give a function which returns @emph{false} to
-indicate a match. The default test function is @code{:test 'eql}.
-
-Many functions which take @var{item} and @code{:test} or @code{:test-not}
-arguments also come in @code{-if} and @code{-if-not} varieties,
-where a @var{predicate} function is passed instead of @var{item},
-and sequence elements match if the predicate returns true on them
-(or false in the case of @code{-if-not}). For example:
-
address@hidden
-(remove* 0 seq :test '=) @equiv{} (remove-if 'zerop seq)
address@hidden example
-
address@hidden
-to remove all zeros from sequence @code{seq}.
-
-Some operations can work on a subsequence of the argument sequence;
-these function take @code{:start} and @code{:end} arguments which
-default to zero and the length of the sequence, respectively.
-Only elements between @var{start} (inclusive) and @var{end}
-(exclusive) are affected by the operation. The @var{end} argument
-may be passed @code{nil} to signify the length of the sequence;
-otherwise, both @var{start} and @var{end} must be integers, with
address@hidden <= @var{start} <= @var{end} <= (length @var{seq})}.
-If the function takes two sequence arguments, the limits are
-defined by keywords @code{:start1} and @code{:end1} for the first,
-and @code{:start2} and @code{:end2} for the second.
-
-A few functions accept a @code{:from-end} argument, which, if
address@hidden, causes the operation to go from right-to-left
-through the sequence instead of left-to-right, and a @code{:count}
-argument, which specifies an integer maximum number of elements
-to be removed or otherwise processed.
-
-The sequence functions make no guarantees about the order in
-which the @code{:test}, @code{:test-not}, and @code{:key} functions
-are called on various elements. Therefore, it is a bad idea to depend
-on side effects of these functions. For example, @code{:from-end}
-may cause the sequence to be scanned actually in reverse, or it may
-be scanned forwards but computing a result ``as if'' it were scanned
-backwards. (Some functions, like @code{mapcar*} and @code{every},
address@hidden specify exactly the order in which the function is called
-so side effects are perfectly acceptable in those cases.)
-
-Strings may contain ``text properties'' as well
-as character data. Except as noted, it is undefined whether or
-not text properties are preserved by sequence functions. For
-example, @code{(remove* ?A @var{str})} may or may not preserve
-the properties of the characters copied from @var{str} into the
-result.
-
address@hidden Mapping over Sequences, Sequence Functions, Sequence Basics,
Sequences
address@hidden Mapping over Sequences
-
address@hidden
-These functions ``map'' the function you specify over the elements
-of lists or arrays. They are all variations on the theme of the
-built-in function @code{mapcar}.
-
address@hidden mapcar* function seq &rest more-seqs
-This function calls @var{function} on successive parallel sets of
-elements from its argument sequences. Given a single @var{seq}
-argument it is equivalent to @code{mapcar}; given @var{n} sequences,
-it calls the function with the first elements of each of the sequences
-as the @var{n} arguments to yield the first element of the result
-list, then with the second elements, and so on. The mapping stops as
-soon as the shortest sequence runs out. The argument sequences may
-be any mixture of lists, strings, and vectors; the return sequence
-is always a list.
-
-Common Lisp's @code{mapcar} accepts multiple arguments but works
-only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
-argument. This package's @code{mapcar*} works as a compatible
-superset of both.
address@hidden defun
-
address@hidden map result-type function seq &rest more-seqs
-This function maps @var{function} over the argument sequences,
-just like @code{mapcar*}, but it returns a sequence of type
address@hidden rather than a list. @var{result-type} must
-be one of the following symbols: @code{vector}, @code{string},
address@hidden (in which case the effect is the same as for
address@hidden), or @code{nil} (in which case the results are
-thrown away and @code{map} returns @code{nil}).
address@hidden defun
-
address@hidden maplist function list &rest more-lists
-This function calls @var{function} on each of its argument lists,
-then on the @code{cdr}s of those lists, and so on, until the
-shortest list runs out. The results are returned in the form
-of a list. Thus, @code{maplist} is like @code{mapcar*} except
-that it passes in the list pointers themselves rather than the
address@hidden of the advancing pointers.
address@hidden defun
-
address@hidden mapc function seq &rest more-seqs
-This function is like @code{mapcar*}, except that the values returned
-by @var{function} are ignored and thrown away rather than being
-collected into a list. The return value of @code{mapc} is @var{seq},
-the first sequence. This function is more general than the Emacs
-primitive @code{mapc}.
address@hidden defun
-
address@hidden mapl function list &rest more-lists
-This function is like @code{maplist}, except that it throws away
-the values returned by @var{function}.
address@hidden defun
-
address@hidden mapcan function seq &rest more-seqs
-This function is like @code{mapcar*}, except that it concatenates
-the return values (which must be lists) using @code{nconc},
-rather than simply collecting them into a list.
address@hidden defun
-
address@hidden mapcon function list &rest more-lists
-This function is like @code{maplist}, except that it concatenates
-the return values using @code{nconc}.
address@hidden defun
-
address@hidden some predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of @var{seq}
-in turn; if @var{predicate} returns a address@hidden value,
address@hidden returns that value, otherwise it returns @code{nil}.
-Given several sequence arguments, it steps through the sequences
-in parallel until the shortest one runs out, just as in
address@hidden You can rely on the left-to-right order in which
-the elements are visited, and on the fact that mapping stops
-immediately as soon as @var{predicate} returns address@hidden
address@hidden defun
-
address@hidden every predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns @code{nil} as soon as @var{predicate} returns
address@hidden for any element, or @code{t} if the predicate was true
-for all elements.
address@hidden defun
-
address@hidden notany predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns @code{nil} as soon as @var{predicate} returns
-a address@hidden value for any element, or @code{t} if the predicate
-was @code{nil} for all elements.
address@hidden defun
-
address@hidden notevery predicate seq &rest more-seqs
-This function calls @var{predicate} on each element of the sequence(s)
-in turn; it returns a address@hidden value as soon as @var{predicate}
-returns @code{nil} for any element, or @code{t} if the predicate was
-true for all elements.
address@hidden defun
-
address@hidden reduce function seq @t{&key :from-end :start :end :initial-value
:key}
-This function combines the elements of @var{seq} using an associative
-binary operation. Suppose @var{function} is @code{*} and @var{seq} is
-the list @code{(2 3 4 5)}. The first two elements of the list are
-combined with @code{(* 2 3) = 6}; this is combined with the next
-element, @code{(* 6 4) = 24}, and that is combined with the final
-element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
-to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
-an explicit call to @code{reduce}.
-
-If @code{:from-end} is true, the reduction is right-associative instead
-of left-associative:
-
address@hidden
-(reduce '- '(1 2 3 4))
- @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
-(reduce '- '(1 2 3 4) :from-end t)
- @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
address@hidden example
-
-If @code{:key} is specified, it is a function of one argument which
-is called on each of the sequence elements in turn.
-
-If @code{:initial-value} is specified, it is effectively added to the
-front (or rear in the case of @code{:from-end}) of the sequence.
-The @code{:key} function is @emph{not} applied to the initial value.
-
-If the sequence, including the initial value, has exactly one element
-then that element is returned without ever calling @var{function}.
-If the sequence is empty (and there is no initial value), then
address@hidden is called with no arguments to obtain the return value.
address@hidden defun
-
-All of these mapping operations can be expressed conveniently in
-terms of the @code{loop} macro. In compiled code, @code{loop} will
-be faster since it generates the loop as in-line code with no
-function calls.
-
address@hidden Sequence Functions, Searching Sequences, Mapping over Sequences,
Sequences
address@hidden Sequence Functions
-
address@hidden
-This section describes a number of Common Lisp functions for
-operating on sequences.
-
address@hidden subseq sequence start &optional end
-This function returns a given subsequence of the argument
address@hidden, which may be a list, string, or vector.
-The indices @var{start} and @var{end} must be in range, and
address@hidden must be no greater than @var{end}. If @var{end}
-is omitted, it defaults to the length of the sequence. The
-return value is always a copy; it does not share structure
-with @var{sequence}.
-
-As an extension to Common Lisp, @var{start} and/or @var{end}
-may be negative, in which case they represent a distance back
-from the end of the sequence. This is for compatibility with
-Emacs' @code{substring} function. Note that @code{subseq} is
-the @emph{only} sequence function that allows negative
address@hidden and @var{end}.
-
-You can use @code{setf} on a @code{subseq} form to replace a
-specified range of elements with elements from another sequence.
-The replacement is done as if by @code{replace}, described below.
address@hidden defun
-
address@hidden concatenate result-type &rest seqs
-This function concatenates the argument sequences together to
-form a result sequence of type @var{result-type}, one of the
-symbols @code{vector}, @code{string}, or @code{list}. The
-arguments are always copied, even in cases such as
address@hidden(concatenate 'list '(1 2 3))} where the result is
-identical to an argument.
address@hidden defun
-
address@hidden fill seq item @t{&key :start :end}
-This function fills the elements of the sequence (or the specified
-part of the sequence) with the value @var{item}.
address@hidden defun
-
address@hidden replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
-This function copies part of @var{seq2} into part of @var{seq1}.
-The sequence @var{seq1} is not stretched or resized; the amount
-of data copied is simply the shorter of the source and destination
-(sub)sequences. The function returns @var{seq1}.
-
-If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
-will work correctly even if the regions indicated by the start
-and end arguments overlap. However, if @var{seq1} and @var{seq2}
-are lists which share storage but are not @code{eq}, and the
-start and end arguments specify overlapping regions, the effect
-is undefined.
address@hidden defun
-
address@hidden remove* item seq @t{&key :test :test-not :key :count :start :end
:from-end}
-This returns a copy of @var{seq} with all elements matching
address@hidden removed. The result may share storage with or be
address@hidden to @var{seq} in some circumstances, but the original
address@hidden will not be modified. The @code{:test}, @code{:test-not},
-and @code{:key} arguments define the matching test that is used;
-by default, elements @code{eql} to @var{item} are removed. The
address@hidden:count} argument specifies the maximum number of matching
-elements that can be removed (only the leftmost @var{count} matches
-are removed). The @code{:start} and @code{:end} arguments specify
-a region in @var{seq} in which elements will be removed; elements
-outside that region are not matched or removed. The @code{:from-end}
-argument, if true, says that elements should be deleted from the
-end of the sequence rather than the beginning (this matters only
-if @var{count} was also specified).
address@hidden defun
-
address@hidden delete* item seq @t{&key :test :test-not :key :count :start :end
:from-end}
-This deletes all elements of @var{seq} which match @var{item}.
-It is a destructive operation. Since Emacs Lisp does not support
-stretchable strings or vectors, this is the same as @code{remove*}
-for those sequence types. On lists, @code{remove*} will copy the
-list if necessary to preserve the original list, whereas
address@hidden will splice out parts of the argument list.
-Compare @code{append} and @code{nconc}, which are analogous
-non-destructive and destructive list operations in Emacs Lisp.
address@hidden defun
-
address@hidden remove-if
address@hidden remove-if-not
address@hidden delete-if
address@hidden delete-if-not
-The predicate-oriented functions @code{remove-if}, @code{remove-if-not},
address@hidden, and @code{delete-if-not} are defined similarly.
-
address@hidden remove-duplicates seq @t{&key :test :test-not :key :start :end
:from-end}
-This function returns a copy of @var{seq} with duplicate elements
-removed. Specifically, if two elements from the sequence match
-according to the @code{:test}, @code{:test-not}, and @code{:key}
-arguments, only the rightmost one is retained. If @code{:from-end}
-is true, the leftmost one is retained instead. If @code{:start} or
address@hidden:end} is specified, only elements within that subsequence are
-examined or removed.
address@hidden defun
-
address@hidden delete-duplicates seq @t{&key :test :test-not :key :start :end
:from-end}
-This function deletes duplicate elements from @var{seq}. It is
-a destructive version of @code{remove-duplicates}.
address@hidden defun
-
address@hidden substitute new old seq @t{&key :test :test-not :key :count
:start :end :from-end}
-This function returns a copy of @var{seq}, with all elements
-matching @var{old} replaced with @var{new}. The @code{:count},
address@hidden:start}, @code{:end}, and @code{:from-end} arguments may be
-used to limit the number of substitutions made.
address@hidden defun
-
address@hidden nsubstitute new old seq @t{&key :test :test-not :key :count
:start :end :from-end}
-This is a destructive version of @code{substitute}; it performs
-the substitution using @code{setcar} or @code{aset} rather than
-by returning a changed copy of the sequence.
address@hidden defun
-
address@hidden substitute-if
address@hidden substitute-if-not
address@hidden nsubstitute-if
address@hidden nsubstitute-if-not
-The @code{substitute-if}, @code{substitute-if-not}, @code{nsubstitute-if},
-and @code{nsubstitute-if-not} functions are defined similarly. For
-these, a @var{predicate} is given in place of the @var{old} argument.
-
address@hidden Searching Sequences, Sorting Sequences, Sequence Functions,
Sequences
address@hidden Searching Sequences
-
address@hidden
-These functions search for elements or subsequences in a sequence.
-(See also @code{member*} and @code{assoc*}; @pxref{Lists}.)
-
address@hidden find item seq @t{&key :test :test-not :key :start :end :from-end}
-This function searches @var{seq} for an element matching @var{item}.
-If it finds a match, it returns the matching element. Otherwise,
-it returns @code{nil}. It returns the leftmost match, unless
address@hidden:from-end} is true, in which case it returns the rightmost
-match. The @code{:start} and @code{:end} arguments may be used to
-limit the range of elements that are searched.
address@hidden defun
-
address@hidden position item seq @t{&key :test :test-not :key :start :end
:from-end}
-This function is like @code{find}, except that it returns the
-integer position in the sequence of the matching item rather than
-the item itself. The position is relative to the start of the
-sequence as a whole, even if @code{:start} is non-zero. The function
-returns @code{nil} if no matching element was found.
address@hidden defun
-
address@hidden count item seq @t{&key :test :test-not :key :start :end}
-This function returns the number of elements of @var{seq} which
-match @var{item}. The result is always a nonnegative integer.
address@hidden defun
-
address@hidden find-if
address@hidden find-if-not
address@hidden position-if
address@hidden position-if-not
address@hidden count-if
address@hidden count-if-not
-The @code{find-if}, @code{find-if-not}, @code{position-if},
address@hidden, @code{count-if}, and @code{count-if-not}
-functions are defined similarly.
-
address@hidden mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1
:start2 :end2 :from-end}
-This function compares the specified parts of @var{seq1} and
address@hidden If they are the same length and the corresponding
-elements match (according to @code{:test}, @code{:test-not},
-and @code{:key}), the function returns @code{nil}. If there is
-a mismatch, the function returns the index (relative to @var{seq1})
-of the first mismatching element. This will be the leftmost pair of
-elements which do not match, or the position at which the shorter of
-the two otherwise-matching sequences runs out.
-
-If @code{:from-end} is true, then the elements are compared from right
-to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
-If the sequences differ, then one plus the index of the rightmost
-difference (relative to @var{seq1}) is returned.
-
-An interesting example is @code{(mismatch str1 str2 :key 'upcase)},
-which compares two strings case-insensitively.
address@hidden defun
-
address@hidden search seq1 seq2 @t{&key :test :test-not :key :from-end :start1
:end1 :start2 :end2}
-This function searches @var{seq2} for a subsequence that matches
address@hidden (or part of it specified by @code{:start1} and
address@hidden:end1}.) Only matches which fall entirely within the region
-defined by @code{:start2} and @code{:end2} will be considered.
-The return value is the index of the leftmost element of the
-leftmost match, relative to the start of @var{seq2}, or @code{nil}
-if no matches were found. If @code{:from-end} is true, the
-function finds the @emph{rightmost} matching subsequence.
address@hidden defun
-
address@hidden Sorting Sequences, , Searching Sequences, Sequences
address@hidden Sorting Sequences
-
address@hidden sort* seq predicate @t{&key :key}
-This function sorts @var{seq} into increasing order as determined
-by using @var{predicate} to compare pairs of elements. @var{predicate}
-should return true (address@hidden) if and only if its first argument
-is less than (not equal to) its second argument. For example,
address@hidden<} and @code{string-lessp} are suitable predicate functions
-for sorting numbers and strings, respectively; @code{>} would sort
-numbers into decreasing rather than increasing order.
-
-This function differs from Emacs' built-in @code{sort} in that it
-can operate on any type of sequence, not just lists. Also, it
-accepts a @code{:key} argument which is used to preprocess data
-fed to the @var{predicate} function. For example,
-
address@hidden
-(setq data (sort* data 'string-lessp :key 'downcase))
address@hidden example
-
address@hidden
-sorts @var{data}, a sequence of strings, into increasing alphabetical
-order without regard to case. A @code{:key} function of @code{car}
-would be useful for sorting association lists. It should only be a
-simple accessor though, it's used heavily in the current
-implementation.
-
-The @code{sort*} function is destructive; it sorts lists by actually
-rearranging the @code{cdr} pointers in suitable fashion.
address@hidden defun
-
address@hidden stable-sort seq predicate @t{&key :key}
-This function sorts @var{seq} @dfn{stably}, meaning two elements
-which are equal in terms of @var{predicate} are guaranteed not to
-be rearranged out of their original order by the sort.
-
-In practice, @code{sort*} and @code{stable-sort} are equivalent
-in Emacs Lisp because the underlying @code{sort} function is
-stable by default. However, this package reserves the right to
-use non-stable methods for @code{sort*} in the future.
address@hidden defun
-
address@hidden merge type seq1 seq2 predicate @t{&key :key}
-This function merges two sequences @var{seq1} and @var{seq2} by
-interleaving their elements. The result sequence, of type @var{type}
-(in the sense of @code{concatenate}), has length equal to the sum
-of the lengths of the two input sequences. The sequences may be
-modified destructively. Order of elements within @var{seq1} and
address@hidden is preserved in the interleaving; elements of the two
-sequences are compared by @var{predicate} (in the sense of
address@hidden) and the lesser element goes first in the result.
-When elements are equal, those from @var{seq1} precede those from
address@hidden in the result. Thus, if @var{seq1} and @var{seq2} are
-both sorted according to @var{predicate}, then the result will be
-a merged sequence which is (stably) sorted according to
address@hidden
address@hidden defun
-
address@hidden Lists, Structures, Sequences, Top
address@hidden Lists
-
address@hidden
-The functions described here operate on lists.
-
address@hidden
-* List Functions:: `caddr', `first', `list*', etc.
-* Substitution of Expressions:: `subst', `sublis', etc.
-* Lists as Sets:: `member*', `adjoin', `union', etc.
-* Association Lists:: `assoc*', `rassoc*', `acons', `pairlis'
address@hidden menu
-
address@hidden List Functions, Substitution of Expressions, Lists, Lists
address@hidden List Functions
-
address@hidden
-This section describes a number of simple operations on lists,
-i.e., chains of cons cells.
-
address@hidden caddr x
-This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
-Likewise, this package defines all 28 @address@hidden functions
-where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
-All of these functions are @code{setf}-able, and calls to them
-are expanded inline by the byte-compiler for maximum efficiency.
address@hidden defun
-
address@hidden first x
-This function is a synonym for @code{(car @var{x})}. Likewise,
-the functions @code{second}, @code{third}, @dots{}, through
address@hidden return the given element of the list @var{x}.
address@hidden defun
-
address@hidden rest x
-This function is a synonym for @code{(cdr @var{x})}.
address@hidden defun
-
address@hidden endp x
-Common Lisp defines this function to act like @code{null}, but
-signaling an error if @code{x} is neither a @code{nil} nor a
-cons cell. This package simply defines @code{endp} as a synonym
-for @code{null}.
address@hidden defun
-
address@hidden list-length x
-This function returns the length of list @var{x}, exactly like
address@hidden(length @var{x})}, except that if @var{x} is a circular
-list (where the cdr-chain forms a loop rather than terminating
-with @code{nil}), this function returns @code{nil}. (The regular
address@hidden function would get stuck if given a circular list.)
address@hidden defun
-
address@hidden list* arg &rest others
-This function constructs a list of its arguments. The final
-argument becomes the @code{cdr} of the last cell constructed.
-Thus, @code{(list* @var{a} @var{b} @var{c})} is equivalent to
address@hidden(cons @var{a} (cons @var{b} @var{c}))}, and
address@hidden(list* @var{a} @var{b} nil)} is equivalent to
address@hidden(list @var{a} @var{b})}.
-
-(Note that this function really is called @code{list*} in Common
-Lisp; it is not a name invented for this package like @code{member*}
-or @code{defun*}.)
address@hidden defun
-
address@hidden ldiff list sublist
-If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to
-one of the cons cells of @var{list}, then this function returns
-a copy of the part of @var{list} up to but not including
address@hidden For example, @code{(ldiff x (cddr x))} returns
-the first two elements of the list @code{x}. The result is a
-copy; the original @var{list} is not modified. If @var{sublist}
-is not a sublist of @var{list}, a copy of the entire @var{list}
-is returned.
address@hidden defun
-
address@hidden copy-list list
-This function returns a copy of the list @var{list}. It copies
-dotted lists like @code{(1 2 . 3)} correctly.
address@hidden defun
-
address@hidden copy-tree x &optional vecp
-This function returns a copy of the tree of cons cells @var{x}.
-Unlike @code{copy-sequence} (and its alias @code{copy-list}),
-which copies only along the @code{cdr} direction, this function
-copies (recursively) along both the @code{car} and the @code{cdr}
-directions. If @var{x} is not a cons cell, the function simply
-returns @var{x} unchanged. If the optional @var{vecp} argument
-is true, this function copies vectors (recursively) as well as
-cons cells.
address@hidden defun
-
address@hidden tree-equal x y @t{&key :test :test-not :key}
-This function compares two trees of cons cells. If @var{x} and
address@hidden are both cons cells, their @code{car}s and @code{cdr}s are
-compared recursively. If neither @var{x} nor @var{y} is a cons
-cell, they are compared by @code{eql}, or according to the
-specified test. The @code{:key} function, if specified, is
-applied to the elements of both trees. @xref{Sequences}.
address@hidden defun
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Substitution of Expressions, Lists as Sets, List Functions, Lists
address@hidden Substitution of Expressions
-
address@hidden
-These functions substitute elements throughout a tree of cons
-cells. (@xref{Sequence Functions}, for the @code{substitute}
-function, which works on just the top-level elements of a list.)
-
address@hidden subst new old tree @t{&key :test :test-not :key}
-This function substitutes occurrences of @var{old} with @var{new}
-in @var{tree}, a tree of cons cells. It returns a substituted
-tree, which will be a copy except that it may share storage with
-the argument @var{tree} in parts where no substitutions occurred.
-The original @var{tree} is not modified. This function recurses
-on, and compares against @var{old}, both @code{car}s and @code{cdr}s
-of the component cons cells. If @var{old} is itself a cons cell,
-then matching cells in the tree are substituted as usual without
-recursively substituting in that cell. Comparisons with @var{old}
-are done according to the specified test (@code{eql} by default).
-The @code{:key} function is applied to the elements of the tree
-but not to @var{old}.
address@hidden defun
-
address@hidden nsubst new old tree @t{&key :test :test-not :key}
-This function is like @code{subst}, except that it works by
-destructive modification (by @code{setcar} or @code{setcdr})
-rather than copying.
address@hidden defun
-
address@hidden subst-if
address@hidden subst-if-not
address@hidden nsubst-if
address@hidden nsubst-if-not
-The @code{subst-if}, @code{subst-if-not}, @code{nsubst-if}, and
address@hidden functions are defined similarly.
-
address@hidden sublis alist tree @t{&key :test :test-not :key}
-This function is like @code{subst}, except that it takes an
-association list @var{alist} of @address@hidden pairs.
-Each element of the tree (after applying the @code{:key}
-function, if any), is compared with the @code{car}s of
address@hidden; if it matches, it is replaced by the corresponding
address@hidden
address@hidden defun
-
address@hidden nsublis alist tree @t{&key :test :test-not :key}
-This is a destructive version of @code{sublis}.
address@hidden defun
-
address@hidden Lists as Sets, Association Lists, Substitution of Expressions,
Lists
address@hidden Lists as Sets
-
address@hidden
-These functions perform operations on lists which represent sets
-of elements.
-
address@hidden member* item list @t{&key :test :test-not :key}
-This function searches @var{list} for an element matching @var{item}.
-If a match is found, it returns the cons cell whose @code{car} was
-the matching element. Otherwise, it returns @code{nil}. Elements
-are compared by @code{eql} by default; you can use the @code{:test},
address@hidden:test-not}, and @code{:key} arguments to modify this behavior.
address@hidden
-
-Note that this function's name is suffixed by @samp{*} to avoid
-the incompatible @code{member} function defined in Emacs.
-(That function uses @code{equal} for comparisons; it is equivalent
-to @code{(member* @var{item} @var{list} :test 'equal)}.)
address@hidden defun
-
address@hidden member-if
address@hidden member-if-not
-The @code{member-if} and @code{member-if-not} functions
-analogously search for elements which satisfy a given predicate.
-
address@hidden tailp sublist list
-This function returns @code{t} if @var{sublist} is a sublist of
address@hidden, i.e., if @var{sublist} is @code{eql} to @var{list} or to
-any of its @code{cdr}s.
address@hidden defun
-
address@hidden adjoin item list @t{&key :test :test-not :key}
-This function conses @var{item} onto the front of @var{list},
-like @code{(cons @var{item} @var{list})}, but only if @var{item}
-is not already present on the list (as determined by @code{member*}).
-If a @code{:key} argument is specified, it is applied to
address@hidden as well as to the elements of @var{list} during
-the search, on the reasoning that @var{item} is ``about'' to
-become part of the list.
address@hidden defun
-
address@hidden union list1 list2 @t{&key :test :test-not :key}
-This function combines two lists which represent sets of items,
-returning a list that represents the union of those two sets.
-The result list will contain all items which appear in @var{list1}
-or @var{list2}, and no others. If an item appears in both
address@hidden and @var{list2} it will be copied only once. If
-an item is duplicated in @var{list1} or @var{list2}, it is
-undefined whether or not that duplication will survive in the
-result list. The order of elements in the result list is also
-undefined.
address@hidden defun
-
address@hidden nunion list1 list2 @t{&key :test :test-not :key}
-This is a destructive version of @code{union}; rather than copying,
-it tries to reuse the storage of the argument lists if possible.
address@hidden defun
-
address@hidden intersection list1 list2 @t{&key :test :test-not :key}
-This function computes the intersection of the sets represented
-by @var{list1} and @var{list2}. It returns the list of items
-which appear in both @var{list1} and @var{list2}.
address@hidden defun
-
address@hidden nintersection list1 list2 @t{&key :test :test-not :key}
-This is a destructive version of @code{intersection}. It
-tries to reuse storage of @var{list1} rather than copying.
-It does @emph{not} reuse the storage of @var{list2}.
address@hidden defun
-
address@hidden set-difference list1 list2 @t{&key :test :test-not :key}
-This function computes the ``set difference'' of @var{list1}
-and @var{list2}, i.e., the set of elements that appear in
address@hidden but @emph{not} in @var{list2}.
address@hidden defun
-
address@hidden nset-difference list1 list2 @t{&key :test :test-not :key}
-This is a destructive @code{set-difference}, which will try
-to reuse @var{list1} if possible.
address@hidden defun
-
address@hidden set-exclusive-or list1 list2 @t{&key :test :test-not :key}
-This function computes the ``set exclusive or'' of @var{list1}
-and @var{list2}, i.e., the set of elements that appear in
-exactly one of @var{list1} and @var{list2}.
address@hidden defun
-
address@hidden nset-exclusive-or list1 list2 @t{&key :test :test-not :key}
-This is a destructive @code{set-exclusive-or}, which will try
-to reuse @var{list1} and @var{list2} if possible.
address@hidden defun
-
address@hidden subsetp list1 list2 @t{&key :test :test-not :key}
-This function checks whether @var{list1} represents a subset
-of @var{list2}, i.e., whether every element of @var{list1}
-also appears in @var{list2}.
address@hidden defun
-
address@hidden Association Lists, , Lists as Sets, Lists
address@hidden Association Lists
-
address@hidden
-An @dfn{association list} is a list representing a mapping from
-one set of values to another; any list whose elements are cons
-cells is an association list.
-
address@hidden assoc* item a-list @t{&key :test :test-not :key}
-This function searches the association list @var{a-list} for an
-element whose @code{car} matches (in the sense of @code{:test},
address@hidden:test-not}, and @code{:key}, or by comparison with @code{eql})
-a given @var{item}. It returns the matching element, if any,
-otherwise @code{nil}. It ignores elements of @var{a-list} which
-are not cons cells. (This corresponds to the behavior of
address@hidden and @code{assoc} in Emacs Lisp; Common Lisp's
address@hidden ignores @code{nil}s but considers any other non-cons
-elements of @var{a-list} to be an error.)
address@hidden defun
-
address@hidden rassoc* item a-list @t{&key :test :test-not :key}
-This function searches for an element whose @code{cdr} matches
address@hidden If @var{a-list} represents a mapping, this applies
-the inverse of the mapping to @var{item}.
address@hidden defun
-
address@hidden assoc-if
address@hidden assoc-if-not
address@hidden rassoc-if
address@hidden rassoc-if-not
-The @code{assoc-if}, @code{assoc-if-not}, @code{rassoc-if},
-and @code{rassoc-if-not} functions are defined similarly.
-
-Two simple functions for constructing association lists are:
-
address@hidden acons key value alist
-This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}.
address@hidden defun
-
address@hidden pairlis keys values &optional alist
-This is equivalent to @code{(nconc (mapcar* 'cons @var{keys} @var{values})
address@hidden)}.
address@hidden defun
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Structures, Assertions, Lists, Top
address@hidden Structures
-
address@hidden
-The Common Lisp @dfn{structure} mechanism provides a general way
-to define data types similar to C's @code{struct} types. A
-structure is a Lisp object containing some number of @dfn{slots},
-each of which can hold any Lisp data object. Functions are
-provided for accessing and setting the slots, creating or copying
-structure objects, and recognizing objects of a particular structure
-type.
-
-In true Common Lisp, each structure type is a new type distinct
-from all existing Lisp types. Since the underlying Emacs Lisp
-system provides no way to create new distinct types, this package
-implements structures as vectors (or lists upon request) with a
-special ``tag'' symbol to identify them.
-
address@hidden defstruct name address@hidden
-The @code{defstruct} form defines a new structure type called
address@hidden, with the specified @var{slots}. (The @var{slots}
-may begin with a string which documents the structure type.)
-In the simplest case, @var{name} and each of the @var{slots}
-are symbols. For example,
-
address@hidden
-(defstruct person name age sex)
address@hidden example
-
address@hidden
-defines a struct type called @code{person} which contains three
-slots. Given a @code{person} object @var{p}, you can access those
-slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
-and @code{(person-sex @var{p})}. You can also change these slots by
-using @code{setf} on any of these place forms:
-
address@hidden
-(incf (person-age birthday-boy))
address@hidden example
-
-You can create a new @code{person} by calling @code{make-person},
-which takes keyword arguments @code{:name}, @code{:age}, and
address@hidden:sex} to specify the initial values of these slots in the
-new object. (Omitting any of these arguments leaves the corresponding
-slot ``undefined,'' according to the Common Lisp standard; in Emacs
-Lisp, such uninitialized slots are filled with @code{nil}.)
-
-Given a @code{person}, @code{(copy-person @var{p})} makes a new
-object of the same type whose slots are @code{eq} to those of @var{p}.
-
-Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
-true if @var{x} looks like a @code{person}, false otherwise. (Again,
-in Common Lisp this predicate would be exact; in Emacs Lisp the
-best it can do is verify that @var{x} is a vector of the correct
-length which starts with the correct tag symbol.)
-
-Accessors like @code{person-name} normally check their arguments
-(effectively using @code{person-p}) and signal an error if the
-argument is the wrong type. This check is affected by
address@hidden(optimize (safety @dots{}))} declarations. Safety level 1,
-the default, uses a somewhat optimized check that will detect all
-incorrect arguments, but may use an uninformative error message
-(e.g., ``expected a vector'' instead of ``expected a @code{person}'').
-Safety level 0 omits all checks except as provided by the underlying
address@hidden call; safety levels 2 and 3 do rigorous checking that will
-always print a descriptive error message for incorrect inputs.
address@hidden
-
address@hidden
-(setq dave (make-person :name "Dave" :sex 'male))
- @result{} [cl-struct-person "Dave" nil male]
-(setq other (copy-person dave))
- @result{} [cl-struct-person "Dave" nil male]
-(eq dave other)
- @result{} nil
-(eq (person-name dave) (person-name other))
- @result{} t
-(person-p dave)
- @result{} t
-(person-p [1 2 3 4])
- @result{} nil
-(person-p "Bogus")
- @result{} nil
-(person-p '[cl-struct-person counterfeit person object])
- @result{} t
address@hidden example
-
-In general, @var{name} is either a name symbol or a list of a name
-symbol followed by any number of @dfn{struct options}; each @var{slot}
-is either a slot symbol or a list of the form @samp{(@var{slot-name}
address@hidden @address@hidden)}. The @var{default-value}
-is a Lisp form which is evaluated any time an instance of the
-structure type is created without specifying that slot's value.
-
-Common Lisp defines several slot options, but the only one
-implemented in this package is @code{:read-only}. A address@hidden
-value for this option means the slot should not be @code{setf}-able;
-the slot's value is determined when the object is created and does
-not change afterward.
-
address@hidden
-(defstruct person
- (name nil :read-only t)
- age
- (sex 'unknown))
address@hidden example
-
-Any slot options other than @code{:read-only} are ignored.
-
-For obscure historical reasons, structure options take a different
-form than slot options. A structure option is either a keyword
-symbol, or a list beginning with a keyword symbol possibly followed
-by arguments. (By contrast, slot options are key-value pairs not
-enclosed in lists.)
-
address@hidden
-(defstruct (person (:constructor create-person)
- (:type list)
- :named)
- name age sex)
address@hidden example
-
-The following structure options are recognized.
-
address@hidden @code
address@hidden
address@hidden in
address@hidden@address@hidden
address@hidden iftex
address@hidden :conc-name
-The argument is a symbol whose print name is used as the prefix for
-the names of slot accessor functions. The default is the name of
-the struct type followed by a hyphen. The option @code{(:conc-name p-)}
-would change this prefix to @code{p-}. Specifying @code{nil} as an
-argument means no prefix, so that the slot names themselves are used
-to name the accessor functions.
-
address@hidden :constructor
-In the simple case, this option takes one argument which is an
-alternate name to use for the constructor function. The default
-is @address@hidden, e.g., @code{make-person}. The above
-example changes this to @code{create-person}. Specifying @code{nil}
-as an argument means that no standard constructor should be
-generated at all.
-
-In the full form of this option, the constructor name is followed
-by an arbitrary argument list. @xref{Program Structure}, for a
-description of the format of Common Lisp argument lists. All
-options, such as @code{&rest} and @code{&key}, are supported.
-The argument names should match the slot names; each slot is
-initialized from the corresponding argument. Slots whose names
-do not appear in the argument list are initialized based on the
address@hidden in their slot descriptor. Also, @code{&optional}
-and @code{&key} arguments which don't specify defaults take their
-defaults from the slot descriptor. It is valid to include arguments
-which don't correspond to slot names; these are useful if they are
-referred to in the defaults for optional, keyword, or @code{&aux}
-arguments which @emph{do} correspond to slots.
-
-You can specify any number of full-format @code{:constructor}
-options on a structure. The default constructor is still generated
-as well unless you disable it with a simple-format @code{:constructor}
-option.
-
address@hidden
-(defstruct
- (person
- (:constructor nil) ; no default constructor
- (:constructor new-person (name sex &optional (age 0)))
- (:constructor new-hound (&key (name "Rover")
- (dog-years 0)
- &aux (age (* 7 dog-years))
- (sex 'canine))))
- name age sex)
address@hidden example
-
-The first constructor here takes its arguments positionally rather
-than by keyword. (In official Common Lisp terminology, constructors
-that work By Order of Arguments instead of by keyword are called
-``BOA constructors.'' No, I'm not making this up.) For example,
address@hidden(new-person "Jane" 'female)} generates a person whose slots
-are @code{"Jane"}, 0, and @code{female}, respectively.
-
-The second constructor takes two keyword arguments, @code{:name},
-which initializes the @code{name} slot and defaults to @code{"Rover"},
-and @code{:dog-years}, which does not itself correspond to a slot
-but which is used to initialize the @code{age} slot. The @code{sex}
-slot is forced to the symbol @code{canine} with no syntax for
-overriding it.
-
address@hidden :copier
-The argument is an alternate name for the copier function for
-this type. The default is @address@hidden @code{nil}
-means not to generate a copier function. (In this implementation,
-all copier functions are simply synonyms for @code{copy-sequence}.)
-
address@hidden :predicate
-The argument is an alternate name for the predicate which recognizes
-objects of this type. The default is @address@hidden @code{nil}
-means not to generate a predicate function. (If the @code{:type}
-option is used without the @code{:named} option, no predicate is
-ever generated.)
-
-In true Common Lisp, @code{typep} is always able to recognize a
-structure object even if @code{:predicate} was used. In this
-package, @code{typep} simply looks for a function called
address@hidden@var{typename}-p}, so it will work for structure types
-only if they used the default predicate name.
-
address@hidden :include
-This option implements a very limited form of C++-style inheritance.
-The argument is the name of another structure type previously
-created with @code{defstruct}. The effect is to cause the new
-structure type to inherit all of the included structure's slots
-(plus, of course, any new slots described by this struct's slot
-descriptors). The new structure is considered a ``specialization''
-of the included one. In fact, the predicate and slot accessors
-for the included type will also accept objects of the new type.
-
-If there are extra arguments to the @code{:include} option after
-the included-structure name, these options are treated as replacement
-slot descriptors for slots in the included structure, possibly with
-modified default values. Borrowing an example from Steele:
-
address@hidden
-(defstruct person name (age 0) sex)
- @result{} person
-(defstruct (astronaut (:include person (age 45)))
- helmet-size
- (favorite-beverage 'tang))
- @result{} astronaut
-
-(setq joe (make-person :name "Joe"))
- @result{} [cl-struct-person "Joe" 0 nil]
-(setq buzz (make-astronaut :name "Buzz"))
- @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang]
-
-(list (person-p joe) (person-p buzz))
- @result{} (t t)
-(list (astronaut-p joe) (astronaut-p buzz))
- @result{} (nil t)
-
-(person-name buzz)
- @result{} "Buzz"
-(astronaut-name joe)
- @result{} error: "astronaut-name accessing a non-astronaut"
address@hidden example
-
-Thus, if @code{astronaut} is a specialization of @code{person},
-then every @code{astronaut} is also a @code{person} (but not the
-other way around). Every @code{astronaut} includes all the slots
-of a @code{person}, plus extra slots that are specific to
-astronauts. Operations that work on people (like @code{person-name})
-work on astronauts just like other people.
-
address@hidden :print-function
-In full Common Lisp, this option allows you to specify a function
-which is called to print an instance of the structure type. The
-Emacs Lisp system offers no hooks into the Lisp printer which would
-allow for such a feature, so this package simply ignores
address@hidden:print-function}.
-
address@hidden :type
-The argument should be one of the symbols @code{vector} or @code{list}.
-This tells which underlying Lisp data type should be used to implement
-the new structure type. Vectors are used by default, but
address@hidden(:type list)} will cause structure objects to be stored as
-lists instead.
-
-The vector representation for structure objects has the advantage
-that all structure slots can be accessed quickly, although creating
-vectors is a bit slower in Emacs Lisp. Lists are easier to create,
-but take a relatively long time accessing the later slots.
-
address@hidden :named
-This option, which takes no arguments, causes a characteristic ``tag''
-symbol to be stored at the front of the structure object. Using
address@hidden:type} without also using @code{:named} will result in a
-structure type stored as plain vectors or lists with no identifying
-features.
-
-The default, if you don't specify @code{:type} explicitly, is to
-use named vectors. Therefore, @code{:named} is only useful in
-conjunction with @code{:type}.
-
address@hidden
-(defstruct (person1) name age sex)
-(defstruct (person2 (:type list) :named) name age sex)
-(defstruct (person3 (:type list)) name age sex)
-
-(setq p1 (make-person1))
- @result{} [cl-struct-person1 nil nil nil]
-(setq p2 (make-person2))
- @result{} (person2 nil nil nil)
-(setq p3 (make-person3))
- @result{} (nil nil nil)
-
-(person1-p p1)
- @result{} t
-(person2-p p2)
- @result{} t
-(person3-p p3)
- @result{} error: function person3-p undefined
address@hidden example
-
-Since unnamed structures don't have tags, @code{defstruct} is not
-able to make a useful predicate for recognizing them. Also,
-accessors like @code{person3-name} will be generated but they
-will not be able to do any type checking. The @code{person3-name}
-function, for example, will simply be a synonym for @code{car} in
-this case. By contrast, @code{person2-name} is able to verify
-that its argument is indeed a @code{person2} object before
-proceeding.
-
address@hidden :initial-offset
-The argument must be a nonnegative integer. It specifies a
-number of slots to be left ``empty'' at the front of the
-structure. If the structure is named, the tag appears at the
-specified position in the list or vector; otherwise, the first
-slot appears at that position. Earlier positions are filled
-with @code{nil} by the constructors and ignored otherwise. If
-the type @code{:include}s another type, then @code{:initial-offset}
-specifies a number of slots to be skipped between the last slot
-of the included type and the first new slot.
address@hidden table
address@hidden defspec
-
-Except as noted, the @code{defstruct} facility of this package is
-entirely compatible with that of Common Lisp.
-
address@hidden
address@hidden
address@hidden iftex
-
address@hidden Assertions, Efficiency Concerns, Structures, Top
address@hidden Assertions and Errors
-
address@hidden
-This section describes two macros that test @dfn{assertions}, i.e.,
-conditions which must be true if the program is operating correctly.
-Assertions never add to the behavior of a Lisp program; they simply
-make ``sanity checks'' to make sure everything is as it should be.
-
-If the optimization property @code{speed} has been set to 3, and
address@hidden is less than 3, then the byte-compiler will optimize
-away the following assertions. Because assertions might be optimized
-away, it is a bad idea for them to include side-effects.
-
address@hidden assert test-form [show-args string address@hidden
-This form verifies that @var{test-form} is true (i.e., evaluates to
-a address@hidden value). If so, it returns @code{nil}. If the test
-is not satisfied, @code{assert} signals an error.
-
-A default error message will be supplied which includes @var{test-form}.
-You can specify a different error message by including a @var{string}
-argument plus optional extra arguments. Those arguments are simply
-passed to @code{error} to signal the error.
-
-If the optional second argument @var{show-args} is @code{t} instead
-of @code{nil}, then the error message (with or without @var{string})
-will also include all non-constant arguments of the top-level
address@hidden For example:
-
address@hidden
-(assert (> x 10) t "x is too small: %d")
address@hidden example
-
-This usage of @var{show-args} is an extension to Common Lisp. In
-true Common Lisp, the second argument gives a list of @var{places}
-which can be @code{setf}'d by the user before continuing from the
-error. Since Emacs Lisp does not support continuable errors, it
-makes no sense to specify @var{places}.
address@hidden defspec
-
address@hidden check-type form type [string]
-This form verifies that @var{form} evaluates to a value of type
address@hidden If so, it returns @code{nil}. If not, @code{check-type}
-signals a @code{wrong-type-argument} error. The default error message
-lists the erroneous value along with @var{type} and @var{form}
-themselves. If @var{string} is specified, it is included in the
-error message in place of @var{type}. For example:
-
address@hidden
-(check-type x (integer 1 *) "a positive integer")
address@hidden example
-
address@hidden Predicates}, for a description of the type specifiers
-that may be used for @var{type}.
-
-Note that in Common Lisp, the first argument to @code{check-type}
-must be a @var{place} suitable for use by @code{setf}, because
address@hidden signals a continuable error that allows the
-user to modify @var{place}.
address@hidden defspec
-
-The following error-related macro is also defined:
-
address@hidden ignore-errors address@hidden
-This executes @var{forms} exactly like a @code{progn}, except that
-errors are ignored during the @var{forms}. More precisely, if
-an error is signaled then @code{ignore-errors} immediately
-aborts execution of the @var{forms} and returns @code{nil}.
-If the @var{forms} complete successfully, @code{ignore-errors}
-returns the result of the last @var{form}.
address@hidden defspec
-
address@hidden Efficiency Concerns, Common Lisp Compatibility, Assertions, Top
address@hidden Efficiency Concerns
-
address@hidden Macros
-
address@hidden
-Many of the advanced features of this package, such as @code{defun*},
address@hidden, and @code{setf}, are implemented as Lisp macros. In
-byte-compiled code, these complex notations will be expanded into
-equivalent Lisp code which is simple and efficient. For example,
-the forms
-
address@hidden
-(incf i n)
-(push x (car p))
address@hidden example
-
address@hidden
-are expanded at compile-time to the Lisp forms
-
address@hidden
-(setq i (+ i n))
-(setcar p (cons x (car p)))
address@hidden example
-
address@hidden
-which are the most efficient ways of doing these respective operations
-in Lisp. Thus, there is no performance penalty for using the more
-readable @code{incf} and @code{push} forms in your compiled code.
-
address@hidden code, on the other hand, must expand these macros
-every time they are executed. For this reason it is strongly
-recommended that code making heavy use of macros be compiled.
-(The features labeled ``Special Form'' instead of ``Function'' in
-this manual are macros.) A loop using @code{incf} a hundred times
-will execute considerably faster if compiled, and will also
-garbage-collect less because the macro expansion will not have
-to be generated, used, and thrown away a hundred times.
-
-You can find out how a macro expands by using the
address@hidden function.
-
address@hidden cl-prettyexpand form &optional full
-This function takes a single Lisp form as an argument and inserts
-a nicely formatted copy of it in the current buffer (which must be
-in Lisp mode so that indentation works properly). It also expands
-all Lisp macros which appear in the form. The easiest way to use
-this function is to go to the @code{*scratch*} buffer and type, say,
-
address@hidden
-(cl-prettyexpand '(loop for x below 10 collect x))
address@hidden example
-
address@hidden
-and type @kbd{C-x C-e} immediately after the closing parenthesis;
-the expansion
-
address@hidden
-(block nil
- (let* ((x 0)
- (G1004 nil))
- (while (< x 10)
- (setq G1004 (cons x G1004))
- (setq x (+ x 1)))
- (nreverse G1004)))
address@hidden example
-
address@hidden
-will be inserted into the buffer. (The @code{block} macro is
-expanded differently in the interpreter and compiler, so
address@hidden just leaves it alone. The temporary
-variable @code{G1004} was created by @code{gensym}.)
-
-If the optional argument @var{full} is true, then @emph{all}
-macros are expanded, including @code{block}, @code{eval-when},
-and compiler macros. Expansion is done as if @var{form} were
-a top-level form in a file being compiled. For example,
-
address@hidden
-(cl-prettyexpand '(pushnew 'x list))
- @print{} (setq list (adjoin 'x list))
-(cl-prettyexpand '(pushnew 'x list) t)
- @print{} (setq list (if (memq 'x list) list (cons 'x list)))
-(cl-prettyexpand '(caddr (member* 'a list)) t)
- @print{} (car (cdr (cdr (memq 'a list))))
address@hidden example
-
-Note that @code{adjoin}, @code{caddr}, and @code{member*} all
-have built-in compiler macros to optimize them in common cases.
address@hidden defun
-
address@hidden
address@hidden
-
address@hidden example
address@hidden ifinfo
address@hidden Error Checking
-
address@hidden
-Common Lisp compliance has in general not been sacrificed for the
-sake of efficiency. A few exceptions have been made for cases
-where substantial gains were possible at the expense of marginal
-incompatibility.
-
-The Common Lisp standard (as embodied in Steele's book) uses the
-phrase ``it is an error if'' to indicate a situation which is not
-supposed to arise in complying programs; implementations are strongly
-encouraged but not required to signal an error in these situations.
-This package sometimes omits such error checking in the interest of
-compactness and efficiency. For example, @code{do} variable
-specifiers are supposed to be lists of one, two, or three forms;
-extra forms are ignored by this package rather than signaling a
-syntax error. The @code{endp} function is simply a synonym for
address@hidden in this package. Functions taking keyword arguments
-will accept an odd number of arguments, treating the trailing
-keyword as if it were followed by the value @code{nil}.
-
-Argument lists (as processed by @code{defun*} and friends)
address@hidden checked rigorously except for the minor point just
-mentioned; in particular, keyword arguments are checked for
-validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
-are fully implemented. Keyword validity checking is slightly
-time consuming (though not too bad in byte-compiled code);
-you can use @code{&allow-other-keys} to omit this check. Functions
-defined in this package such as @code{find} and @code{member*}
-do check their keyword arguments for validity.
-
address@hidden
address@hidden
-
address@hidden example
address@hidden ifinfo
address@hidden Optimizing Compiler
-
address@hidden
-Use of the optimizing Emacs compiler is highly recommended; many of the Common
-Lisp macros emit
-code which can be improved by optimization. In particular,
address@hidden (whether explicit or implicit in constructs like
address@hidden and @code{loop}) carry a fair run-time penalty; the
-optimizing compiler removes @code{block}s which are not actually
-referenced by @code{return} or @code{return-from} inside the block.
-
address@hidden Common Lisp Compatibility, Old CL Compatibility, Efficiency
Concerns, Top
address@hidden Common Lisp Compatibility
-
address@hidden
-Following is a list of all known incompatibilities between this
-package and Common Lisp as documented in Steele (2nd edition).
-
-Certain function names, such as @code{member}, @code{assoc}, and
address@hidden, were already taken by (incompatible) Emacs Lisp
-functions; this package appends @samp{*} to the names of its
-Common Lisp versions of these functions.
-
-The word @code{defun*} is required instead of @code{defun} in order
-to use extended Common Lisp argument lists in a function. Likewise,
address@hidden and @code{function*} are versions of those forms
-which understand full-featured argument lists. The @code{&whole}
-keyword does not work in @code{defmacro} argument lists (except
-inside recursive argument lists).
-
-The @code{eql} and @code{equal} predicates do not distinguish
-between IEEE floating-point plus and minus zero. The @code{equalp}
-predicate has several differences with Common Lisp; @pxref{Predicates}.
-
-The @code{setf} mechanism is entirely compatible, except that
-setf-methods return a list of five values rather than five
-values directly. Also, the new address@hidden function'' concept
-(typified by @code{(defun (setf foo) @dots{})}) is not implemented.
-
-The @code{do-all-symbols} form is the same as @code{do-symbols}
-with no @var{obarray} argument. In Common Lisp, this form would
-iterate over all symbols in all packages. Since Emacs obarrays
-are not a first-class package mechanism, there is no way for
address@hidden to locate any but the default obarray.
-
-The @code{loop} macro is complete except that @code{loop-finish}
-and type specifiers are unimplemented.
-
-The multiple-value return facility treats lists as multiple
-values, since Emacs Lisp cannot support multiple return values
-directly. The macros will be compatible with Common Lisp if
address@hidden or @code{values-list} is always used to return to
-a @code{multiple-value-bind} or other multiple-value receiver;
-if @code{values} is used without @address@hidden
-or vice-versa the effect will be different from Common Lisp.
-
-Many Common Lisp declarations are ignored, and others match
-the Common Lisp standard in concept but not in detail. For
-example, local @code{special} declarations, which are purely
-advisory in Emacs Lisp, do not rigorously obey the scoping rules
-set down in Steele's book.
-
-The variable @code{*gensym-counter*} starts out with a pseudo-random
-value rather than with zero. This is to cope with the fact that
-generated symbols become interned when they are written to and
-loaded back from a file.
-
-The @code{defstruct} facility is compatible, except that structures
-are of type @code{:type vector :named} by default rather than some
-special, distinct type. Also, the @code{:type} slot option is ignored.
-
-The second argument of @code{check-type} is treated differently.
-
address@hidden Old CL Compatibility, Porting Common Lisp, Common Lisp
Compatibility, Top
address@hidden Old CL Compatibility
-
address@hidden
-Following is a list of all known incompatibilities between this package
-and the older Quiroz @file{cl.el} package.
-
-This package's emulation of multiple return values in functions is
-incompatible with that of the older package. That package attempted
-to come as close as possible to true Common Lisp multiple return
-values; unfortunately, it could not be 100% reliable and so was prone
-to occasional surprises if used freely. This package uses a simpler
-method, namely replacing multiple values with lists of values, which
-is more predictable though more noticeably different from Common Lisp.
-
-The @code{defkeyword} form and @code{keywordp} function are not
-implemented in this package.
-
-The @code{member}, @code{floor}, @code{ceiling}, @code{truncate},
address@hidden, @code{mod}, and @code{rem} functions are suffixed
-by @samp{*} in this package to avoid collision with existing
-functions in Emacs. The older package simply
-redefined these functions, overwriting the built-in meanings and
-causing serious portability problems. (Some more
-recent versions of the Quiroz package changed the names to
address@hidden, etc.; this package defines the latter names as
-aliases for @code{member*}, etc.)
-
-Certain functions in the old package which were buggy or inconsistent
-with the Common Lisp standard are incompatible with the conforming
-versions in this package. For example, @code{eql} and @code{member}
-were synonyms for @code{eq} and @code{memq} in that package, @code{setf}
-failed to preserve correct order of evaluation of its arguments, etc.
-
-Finally, unlike the older package, this package is careful to
-prefix all of its internal names with @code{cl-}. Except for a
-few functions which are explicitly defined as additional features
-(such as @code{floatp-safe} and @code{letf}), this package does not
-export any address@hidden symbols which are not also part of Common
-Lisp.
-
address@hidden
address@hidden
-
address@hidden example
address@hidden ifinfo
address@hidden The @code{cl-compat} package
-
address@hidden
-The @dfn{CL} package includes emulations of some features of the
-old @file{cl.el}, in the form of a compatibility package
address@hidden To use it, put @code{(require 'cl-compat)} in
-your program.
-
-The old package defined a number of internal routines without
address@hidden prefixes or other annotations. Call to these routines
-may have crept into existing Lisp code. @code{cl-compat}
-provides emulations of the following internal routines:
address@hidden, @code{zip-lists}, @code{unzip-lists},
address@hidden, @code{duplicate-symbols-p},
address@hidden
-
-Some @code{setf} forms translated into calls to internal
-functions that user code might call directly. The functions
address@hidden, @code{setnthcdr}, and @code{setelt} fall in
-this category; they are defined by @code{cl-compat}, but the
-best fix is to change to use @code{setf} properly.
-
-The @code{cl-compat} file defines the keyword functions
address@hidden, @code{keyword-of}, and @code{defkeyword},
-which are not defined by the new @dfn{CL} package because the
-use of keywords as data is discouraged.
-
-The @code{build-klist} mechanism for parsing keyword arguments
-is emulated by @code{cl-compat}; the @code{with-keyword-args}
-macro is not, however, and in any case it's best to change to
-use the more natural keyword argument processing offered by
address@hidden
-
-Multiple return values are treated differently by the two
-Common Lisp packages. The old package's method was more
-compatible with true Common Lisp, though it used heuristics
-that caused it to report spurious multiple return values in
-certain cases. The @code{cl-compat} package defines a set
-of multiple-value macros that are compatible with the old
-CL package; again, they are heuristic in nature, but they
-are guaranteed to work in any case where the old package's
-macros worked. To avoid name collision with the ``official''
-multiple-value facilities, the ones in @code{cl-compat} have
-capitalized names: @code{Values}, @code{Values-list},
address@hidden, etc.
-
-The functions @code{cl-floor}, @code{cl-ceiling}, @code{cl-truncate},
-and @code{cl-round} are defined by @code{cl-compat} to use the
-old-style multiple-value mechanism, just as they did in the old
-package. The newer @code{floor*} and friends return their two
-results in a list rather than as multiple values. Note that
-older versions of the old package used the unadorned names
address@hidden, @code{ceiling}, etc.; @code{cl-compat} cannot use
-these names because they conflict with Emacs built-ins.
-
address@hidden Porting Common Lisp, GNU Free Documentation License, Old CL
Compatibility, Top
address@hidden Porting Common Lisp
-
address@hidden
-This package is meant to be used as an extension to Emacs Lisp,
-not as an Emacs implementation of true Common Lisp. Some of the
-remaining differences between Emacs Lisp and Common Lisp make it
-difficult to port large Common Lisp applications to Emacs. For
-one, some of the features in this package are not fully compliant
-with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
-are also quite a few features that this package does not provide
-at all. Here are some major omissions that you will want to watch out
-for when bringing Common Lisp code into Emacs.
-
address@hidden @bullet
address@hidden
-Case-insensitivity. Symbols in Common Lisp are case-insensitive
-by default. Some programs refer to a function or variable as
address@hidden in one place and @code{Foo} or @code{FOO} in another.
-Emacs Lisp will treat these as three distinct symbols.
-
-Some Common Lisp code is written entirely in upper case. While Emacs
-is happy to let the program's own functions and variables use
-this convention, calls to Lisp builtins like @code{if} and
address@hidden will have to be changed to lower case.
-
address@hidden
-Lexical scoping. In Common Lisp, function arguments and @code{let}
-bindings apply only to references physically within their bodies
-(or within macro expansions in their bodies). Emacs Lisp, by
-contrast, uses @dfn{dynamic scoping} wherein a binding to a
-variable is visible even inside functions called from the body.
-
-Variables in Common Lisp can be made dynamically scoped by
-declaring them @code{special} or using @code{defvar}. In Emacs
-Lisp it is as if all variables were declared @code{special}.
-
-Often you can use code that was written for lexical scoping
-even in a dynamically scoped Lisp, but not always. Here is
-an example of a Common Lisp code fragment that would fail in
-Emacs Lisp:
-
address@hidden
-(defun map-odd-elements (func list)
- (loop for x in list
- for flag = t then (not flag)
- collect (if flag x (funcall func x))))
-
-(defun add-odd-elements (list x)
- (map-odd-elements (lambda (a) (+ a x))) list)
address@hidden example
-
address@hidden
-In Common Lisp, the two functions' usages of @code{x} are completely
-independent. In Emacs Lisp, the binding to @code{x} made by
address@hidden will have been hidden by the binding
-in @code{map-odd-elements} by the time the @code{(+ a x)} function
-is called.
-
-(This package avoids such problems in its own mapping functions
-by using names like @code{cl-x} instead of @code{x} internally;
-as long as you don't use the @code{cl-} prefix for your own
-variables no collision can occur.)
-
address@hidden Bindings}, for a description of the @code{lexical-let}
-form which establishes a Common Lisp-style lexical binding, and some
-examples of how it differs from Emacs' regular @code{let}.
-
address@hidden
-Reader macros. Common Lisp includes a second type of macro that
-works at the level of individual characters. For example, Common
-Lisp implements the quote notation by a reader macro called @code{'},
-whereas Emacs Lisp's parser just treats quote as a special case.
-Some Lisp packages use reader macros to create special syntaxes
-for themselves, which the Emacs parser is incapable of reading.
-
-The lack of reader macros, incidentally, is the reason behind
-Emacs Lisp's unusual backquote syntax. Since backquotes are
-implemented as a Lisp package and not built-in to the Emacs
-parser, they are forced to use a regular macro named @code{`}
-which is used with the standard function/macro call notation.
-
address@hidden
-Other syntactic features. Common Lisp provides a number of
-notations beginning with @code{#} that the Emacs Lisp parser
-won't understand. For example, @samp{#| ... |#} is an
-alternate comment notation, and @samp{#+lucid (foo)} tells
-the parser to ignore the @code{(foo)} except in Lucid Common
-Lisp.
-
address@hidden
-Packages. In Common Lisp, symbols are divided into @dfn{packages}.
-Symbols that are Lisp built-ins are typically stored in one package;
-symbols that are vendor extensions are put in another, and each
-application program would have a package for its own symbols.
-Certain symbols are ``exported'' by a package and others are
-internal; certain packages ``use'' or import the exported symbols
-of other packages. To access symbols that would not normally be
-visible due to this importing and exporting, Common Lisp provides
-a syntax like @code{package:symbol} or @code{package::symbol}.
-
-Emacs Lisp has a single namespace for all interned symbols, and
-then uses a naming convention of putting a prefix like @code{cl-}
-in front of the name. Some Emacs packages adopt the Common Lisp-like
-convention of using @code{cl:} or @code{cl::} as the prefix.
-However, the Emacs parser does not understand colons and just
-treats them as part of the symbol name. Thus, while @code{mapcar}
-and @code{lisp:mapcar} may refer to the same symbol in Common
-Lisp, they are totally distinct in Emacs Lisp. Common Lisp
-programs which refer to a symbol by the full name sometimes
-and the short name other times will not port cleanly to Emacs.
-
-Emacs Lisp does have a concept of ``obarrays,'' which are
-package-like collections of symbols, but this feature is not
-strong enough to be used as a true package mechanism.
-
address@hidden
-The @code{format} function is quite different between Common
-Lisp and Emacs Lisp. It takes an additional ``destination''
-argument before the format string. A destination of @code{nil}
-means to format to a string as in Emacs Lisp; a destination
-of @code{t} means to write to the terminal (similar to
address@hidden in Emacs). Also, format control strings are
-utterly different; @code{~} is used instead of @code{%} to
-introduce format codes, and the set of available codes is
-much richer. There are no notations like @code{\n} for
-string literals; instead, @code{format} is used with the
-``newline'' format code, @code{~%}. More advanced formatting
-codes provide such features as paragraph filling, case
-conversion, and even loops and conditionals.
-
-While it would have been possible to implement most of Common
-Lisp @code{format} in this package (under the name @code{format*},
-of course), it was not deemed worthwhile. It would have required
-a huge amount of code to implement even a decent subset of
address@hidden, yet the functionality it would provide over
-Emacs Lisp's @code{format} would rarely be useful.
-
address@hidden
-Vector constants use square brackets in Emacs Lisp, but
address@hidden(a b c)} notation in Common Lisp. To further complicate
-matters, Emacs has its own @code{#(} notation for
-something entirely different---strings with properties.
-
address@hidden
-Characters are distinct from integers in Common Lisp. The
-notation for character constants is also different: @code{#\A}
-instead of @code{?A}. Also, @code{string=} and @code{string-equal}
-are synonyms in Emacs Lisp whereas the latter is case-insensitive
-in Common Lisp.
-
address@hidden
-Data types. Some Common Lisp data types do not exist in Emacs
-Lisp. Rational numbers and complex numbers are not present,
-nor are large integers (all integers are ``fixnums''). All
-arrays are one-dimensional. There are no readtables or pathnames;
-streams are a set of existing data types rather than a new data
-type of their own. Hash tables, random-states, structures, and
-packages (obarrays) are built from Lisp vectors or lists rather
-than being distinct types.
-
address@hidden
-The Common Lisp Object System (CLOS) is not implemented,
-nor is the Common Lisp Condition System. However, the EIEIO package
-from @uref{ftp://ftp.ultranet.com/pub/zappo} does implement some
-CLOS functionality.
-
address@hidden
-Common Lisp features that are completely redundant with Emacs
-Lisp features of a different name generally have not been
-implemented. For example, Common Lisp writes @code{defconstant}
-where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
-takes its arguments in different ways in the two Lisps but does
-exactly the same thing, so this package has not bothered to
-implement a Common Lisp-style @code{make-list}.
-
address@hidden
-A few more notable Common Lisp features not included in this
-package: @code{compiler-let}, @code{tagbody}, @code{prog},
address@hidden/dpb}, @code{parse-integer}, @code{cerror}.
-
address@hidden
-Recursion. While recursion works in Emacs Lisp just like it
-does in Common Lisp, various details of the Emacs Lisp system
-and compiler make recursion much less efficient than it is in
-most Lisps. Some schools of thought prefer to use recursion
-in Lisp over other techniques; they would sum a list of
-numbers using something like
-
address@hidden
-(defun sum-list (list)
- (if list
- (+ (car list) (sum-list (cdr list)))
- 0))
address@hidden example
-
address@hidden
-where a more iteratively-minded programmer might write one of
-these forms:
-
address@hidden
-(let ((total 0)) (dolist (x my-list) (incf total x)) total)
-(loop for x in my-list sum x)
address@hidden example
-
-While this would be mainly a stylistic choice in most Common Lisps,
-in Emacs Lisp you should be aware that the iterative forms are
-much faster than recursion. Also, Lisp programmers will want to
-note that the current Emacs Lisp compiler does not optimize tail
-recursion.
address@hidden itemize
-
address@hidden GNU Free Documentation License, Function Index, Porting Common
Lisp, Top
address@hidden GNU Free Documentation License
address@hidden doclicense.texi
-
address@hidden Function Index, Variable Index, GNU Free Documentation License,
Top
address@hidden Function Index
-
address@hidden fn
-
address@hidden Variable Index, , Function Index, Top
address@hidden Variable Index
-
address@hidden vr
-
address@hidden odd
address@hidden
address@hidden
-
address@hidden
- arch-tag: b61e7200-3bfa-4a70-a9d3-095e152696f8
address@hidden ignore