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[Emacs-diffs] Changes to strings.texi
|
From: |
Glenn Morris |
|
Subject: |
[Emacs-diffs] Changes to strings.texi |
|
Date: |
Thu, 06 Sep 2007 04:14:25 +0000 |
CVSROOT: /sources/emacs
Module name: emacs
Changes by: Glenn Morris <gm> 07/09/06 04:14:25
Index: strings.texi
===================================================================
RCS file: strings.texi
diff -N strings.texi
--- strings.texi 7 Apr 2007 01:52:16 -0000 1.56
+++ /dev/null 1 Jan 1970 00:00:00 -0000
@@ -1,1163 +0,0 @@
address@hidden -*-texinfo-*-
address@hidden This is part of the GNU Emacs Lisp Reference Manual.
address@hidden Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999,
2001,
address@hidden 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation,
Inc.
address@hidden See the file elisp.texi for copying conditions.
address@hidden ../info/strings
address@hidden Strings and Characters, Lists, Numbers, Top
address@hidden node-name, next, previous, up
address@hidden Strings and Characters
address@hidden strings
address@hidden character arrays
address@hidden characters
address@hidden bytes
-
- A string in Emacs Lisp is an array that contains an ordered sequence
-of characters. Strings are used as names of symbols, buffers, and
-files; to send messages to users; to hold text being copied between
-buffers; and for many other purposes. Because strings are so important,
-Emacs Lisp has many functions expressly for manipulating them. Emacs
-Lisp programs use strings more often than individual characters.
-
- @xref{Strings of Events}, for special considerations for strings of
-keyboard character events.
-
address@hidden
-* Basics: String Basics. Basic properties of strings and characters.
-* Predicates for Strings:: Testing whether an object is a string or char.
-* Creating Strings:: Functions to allocate new strings.
-* Modifying Strings:: Altering the contents of an existing string.
-* Text Comparison:: Comparing characters or strings.
-* String Conversion:: Converting to and from characters and strings.
-* Formatting Strings:: @code{format}: Emacs's analogue of @code{printf}.
-* Case Conversion:: Case conversion functions.
-* Case Tables:: Customizing case conversion.
address@hidden menu
-
address@hidden String Basics
address@hidden String and Character Basics
-
- Characters are represented in Emacs Lisp as integers;
-whether an integer is a character or not is determined only by how it is
-used. Thus, strings really contain integers.
-
- The length of a string (like any array) is fixed, and cannot be
-altered once the string exists. Strings in Lisp are @emph{not}
-terminated by a distinguished character code. (By contrast, strings in
-C are terminated by a character with @acronym{ASCII} code 0.)
-
- Since strings are arrays, and therefore sequences as well, you can
-operate on them with the general array and sequence functions.
-(@xref{Sequences Arrays Vectors}.) For example, you can access or
-change individual characters in a string using the functions @code{aref}
-and @code{aset} (@pxref{Array Functions}).
-
- There are two text representations for address@hidden characters in
-Emacs strings (and in buffers): unibyte and multibyte (@pxref{Text
-Representations}). An @acronym{ASCII} character always occupies one byte in a
-string; in fact, when a string is all @acronym{ASCII}, there is no real
-difference between the unibyte and multibyte representations.
-For most Lisp programming, you don't need to be concerned with these two
-representations.
-
- Sometimes key sequences are represented as strings. When a string is
-a key sequence, string elements in the range 128 to 255 represent meta
-characters (which are large integers) rather than character
-codes in the range 128 to 255.
-
- Strings cannot hold characters that have the hyper, super or alt
-modifiers; they can hold @acronym{ASCII} control characters, but no other
-control characters. They do not distinguish case in @acronym{ASCII} control
-characters. If you want to store such characters in a sequence, such as
-a key sequence, you must use a vector instead of a string.
address@hidden Type}, for more information about the representation of meta
-and other modifiers for keyboard input characters.
-
- Strings are useful for holding regular expressions. You can also
-match regular expressions against strings with @code{string-match}
-(@pxref{Regexp Search}). The functions @code{match-string}
-(@pxref{Simple Match Data}) and @code{replace-match} (@pxref{Replacing
-Match}) are useful for decomposing and modifying strings after
-matching regular expressions against them.
-
- Like a buffer, a string can contain text properties for the characters
-in it, as well as the characters themselves. @xref{Text Properties}.
-All the Lisp primitives that copy text from strings to buffers or other
-strings also copy the properties of the characters being copied.
-
- @xref{Text}, for information about functions that display strings or
-copy them into buffers. @xref{Character Type}, and @ref{String Type},
-for information about the syntax of characters and strings.
address@hidden Characters}, for functions to convert between text
-representations and to encode and decode character codes.
-
address@hidden Predicates for Strings
address@hidden The Predicates for Strings
-
-For more information about general sequence and array predicates,
-see @ref{Sequences Arrays Vectors}, and @ref{Arrays}.
-
address@hidden stringp object
-This function returns @code{t} if @var{object} is a string, @code{nil}
-otherwise.
address@hidden defun
-
address@hidden string-or-null-p object
-This function returns @code{t} if @var{object} is a string or nil,
address@hidden otherwise.
address@hidden defun
-
address@hidden char-or-string-p object
-This function returns @code{t} if @var{object} is a string or a
-character (i.e., an integer), @code{nil} otherwise.
address@hidden defun
-
address@hidden Creating Strings
address@hidden Creating Strings
-
- The following functions create strings, either from scratch, or by
-putting strings together, or by taking them apart.
-
address@hidden make-string count character
-This function returns a string made up of @var{count} repetitions of
address@hidden If @var{count} is negative, an error is signaled.
-
address@hidden
-(make-string 5 ?x)
- @result{} "xxxxx"
-(make-string 0 ?x)
- @result{} ""
address@hidden example
-
- Other functions to compare with this one include @code{char-to-string}
-(@pxref{String Conversion}), @code{make-vector} (@pxref{Vectors}), and
address@hidden (@pxref{Building Lists}).
address@hidden defun
-
address@hidden string &rest characters
-This returns a string containing the characters @var{characters}.
-
address@hidden
-(string ?a ?b ?c)
- @result{} "abc"
address@hidden example
address@hidden defun
-
address@hidden substring string start &optional end
-This function returns a new string which consists of those characters
-from @var{string} in the range from (and including) the character at the
-index @var{start} up to (but excluding) the character at the index
address@hidden The first character is at index zero.
-
address@hidden
address@hidden
-(substring "abcdefg" 0 3)
- @result{} "abc"
address@hidden group
address@hidden example
-
address@hidden
-Here the index for @samp{a} is 0, the index for @samp{b} is 1, and the
-index for @samp{c} is 2. Thus, three letters, @samp{abc}, are copied
-from the string @code{"abcdefg"}. The index 3 marks the character
-position up to which the substring is copied. The character whose index
-is 3 is actually the fourth character in the string.
-
-A negative number counts from the end of the string, so that @minus{}1
-signifies the index of the last character of the string. For example:
-
address@hidden
address@hidden
-(substring "abcdefg" -3 -1)
- @result{} "ef"
address@hidden group
address@hidden example
-
address@hidden
-In this example, the index for @samp{e} is @minus{}3, the index for
address@hidden is @minus{}2, and the index for @samp{g} is @minus{}1.
-Therefore, @samp{e} and @samp{f} are included, and @samp{g} is excluded.
-
-When @code{nil} is used for @var{end}, it stands for the length of the
-string. Thus,
-
address@hidden
address@hidden
-(substring "abcdefg" -3 nil)
- @result{} "efg"
address@hidden group
address@hidden example
-
-Omitting the argument @var{end} is equivalent to specifying @code{nil}.
-It follows that @code{(substring @var{string} 0)} returns a copy of all
-of @var{string}.
-
address@hidden
address@hidden
-(substring "abcdefg" 0)
- @result{} "abcdefg"
address@hidden group
address@hidden example
-
address@hidden
-But we recommend @code{copy-sequence} for this purpose (@pxref{Sequence
-Functions}).
-
-If the characters copied from @var{string} have text properties, the
-properties are copied into the new string also. @xref{Text Properties}.
-
address@hidden also accepts a vector for the first argument.
-For example:
-
address@hidden
-(substring [a b (c) "d"] 1 3)
- @result{} [b (c)]
address@hidden example
-
-A @code{wrong-type-argument} error is signaled if @var{start} is not
-an integer or if @var{end} is neither an integer nor @code{nil}. An
address@hidden error is signaled if @var{start} indicates a
-character following @var{end}, or if either integer is out of range
-for @var{string}.
-
-Contrast this function with @code{buffer-substring} (@pxref{Buffer
-Contents}), which returns a string containing a portion of the text in
-the current buffer. The beginning of a string is at index 0, but the
-beginning of a buffer is at index 1.
address@hidden defun
-
address@hidden substring-no-properties string &optional start end
-This works like @code{substring} but discards all text properties from
-the value. Also, @var{start} may be omitted or @code{nil}, which is
-equivalent to 0. Thus, @address@hidden(substring-no-properties
address@hidden)}} returns a copy of @var{string}, with all text
-properties removed.
address@hidden defun
-
address@hidden concat &rest sequences
address@hidden copying strings
address@hidden concatenating strings
-This function returns a new string consisting of the characters in the
-arguments passed to it (along with their text properties, if any). The
-arguments may be strings, lists of numbers, or vectors of numbers; they
-are not themselves changed. If @code{concat} receives no arguments, it
-returns an empty string.
-
address@hidden
-(concat "abc" "-def")
- @result{} "abc-def"
-(concat "abc" (list 120 121) [122])
- @result{} "abcxyz"
-;; @address@hidden is an empty sequence.}
-(concat "abc" nil "-def")
- @result{} "abc-def"
-(concat "The " "quick brown " "fox.")
- @result{} "The quick brown fox."
-(concat)
- @result{} ""
address@hidden example
-
address@hidden
-The @code{concat} function always constructs a new string that is
-not @code{eq} to any existing string.
-
-In Emacs versions before 21, when an argument was an integer (not a
-sequence of integers), it was converted to a string of digits making up
-the decimal printed representation of the integer. This obsolete usage
-no longer works. The proper way to convert an integer to its decimal
-printed form is with @code{format} (@pxref{Formatting Strings}) or
address@hidden (@pxref{String Conversion}).
-
-For information about other concatenation functions, see the
-description of @code{mapconcat} in @ref{Mapping Functions},
address@hidden in @ref{Vector Functions}, and @code{append} in @ref{Building
-Lists}.
address@hidden defun
-
address@hidden split-string string &optional separators omit-nulls
-This function splits @var{string} into substrings at matches for the
-regular expression @var{separators}. Each match for @var{separators}
-defines a splitting point; the substrings between the splitting points
-are made into a list, which is the value returned by
address@hidden
-
-If @var{omit-nulls} is @code{nil}, the result contains null strings
-whenever there are two consecutive matches for @var{separators}, or a
-match is adjacent to the beginning or end of @var{string}. If
address@hidden is @code{t}, these null strings are omitted from the
-result.
-
-If @var{separators} is @code{nil} (or omitted),
-the default is the value of @code{split-string-default-separators}.
-
-As a special case, when @var{separators} is @code{nil} (or omitted),
-null strings are always omitted from the result. Thus:
-
address@hidden
-(split-string " two words ")
- @result{} ("two" "words")
address@hidden example
-
-The result is not @code{("" "two" "words" "")}, which would rarely be
-useful. If you need such a result, use an explicit value for
address@hidden:
-
address@hidden
-(split-string " two words "
- split-string-default-separators)
- @result{} ("" "two" "words" "")
address@hidden example
-
-More examples:
-
address@hidden
-(split-string "Soup is good food" "o")
- @result{} ("S" "up is g" "" "d f" "" "d")
-(split-string "Soup is good food" "o" t)
- @result{} ("S" "up is g" "d f" "d")
-(split-string "Soup is good food" "o+")
- @result{} ("S" "up is g" "d f" "d")
address@hidden example
-
-Empty matches do count, except that @code{split-string} will not look
-for a final empty match when it already reached the end of the string
-using a non-empty match or when @var{string} is empty:
-
address@hidden
-(split-string "aooob" "o*")
- @result{} ("" "a" "" "b" "")
-(split-string "ooaboo" "o*")
- @result{} ("" "" "a" "b" "")
-(split-string "" "")
- @result{} ("")
address@hidden example
-
-However, when @var{separators} can match the empty string,
address@hidden is usually @code{t}, so that the subtleties in the
-three previous examples are rarely relevant:
-
address@hidden
-(split-string "Soup is good food" "o*" t)
- @result{} ("S" "u" "p" " " "i" "s" " " "g" "d" " " "f" "d")
-(split-string "Nice doggy!" "" t)
- @result{} ("N" "i" "c" "e" " " "d" "o" "g" "g" "y" "!")
-(split-string "" "" t)
- @result{} nil
address@hidden example
-
-Somewhat odd, but predictable, behavior can occur for certain
-``non-greedy'' values of @var{separators} that can prefer empty
-matches over non-empty matches. Again, such values rarely occur in
-practice:
-
address@hidden
-(split-string "ooo" "o*" t)
- @result{} nil
-(split-string "ooo" "\\|o+" t)
- @result{} ("o" "o" "o")
address@hidden example
address@hidden defun
-
address@hidden split-string-default-separators
-The default value of @var{separators} for @code{split-string}. Its
-usual value is @address@hidden"[ \f\t\n\r\v]+"}}.
address@hidden defvar
-
address@hidden Modifying Strings
address@hidden Modifying Strings
-
- The most basic way to alter the contents of an existing string is with
address@hidden (@pxref{Array Functions}). @code{(aset @var{string}
address@hidden @var{char})} stores @var{char} into @var{string} at index
address@hidden Each character occupies one or more bytes, and if @var{char}
-needs a different number of bytes from the character already present at
-that index, @code{aset} signals an error.
-
- A more powerful function is @code{store-substring}:
-
address@hidden store-substring string idx obj
-This function alters part of the contents of the string @var{string}, by
-storing @var{obj} starting at index @var{idx}. The argument @var{obj}
-may be either a character or a (smaller) string.
-
-Since it is impossible to change the length of an existing string, it is
-an error if @var{obj} doesn't fit within @var{string}'s actual length,
-or if any new character requires a different number of bytes from the
-character currently present at that point in @var{string}.
address@hidden defun
-
- To clear out a string that contained a password, use
address@hidden:
-
address@hidden clear-string string
-This makes @var{string} a unibyte string and clears its contents to
-zeros. It may also change @var{string}'s length.
address@hidden defun
-
address@hidden 2000
address@hidden Text Comparison
address@hidden Comparison of Characters and Strings
address@hidden string equality
-
address@hidden char-equal character1 character2
-This function returns @code{t} if the arguments represent the same
-character, @code{nil} otherwise. This function ignores differences
-in case if @code{case-fold-search} is address@hidden
-
address@hidden
-(char-equal ?x ?x)
- @result{} t
-(let ((case-fold-search nil))
- (char-equal ?x ?X))
- @result{} nil
address@hidden example
address@hidden defun
-
address@hidden string= string1 string2
-This function returns @code{t} if the characters of the two strings
-match exactly. Symbols are also allowed as arguments, in which case
-their print names are used.
-Case is always significant, regardless of @code{case-fold-search}.
-
address@hidden
-(string= "abc" "abc")
- @result{} t
-(string= "abc" "ABC")
- @result{} nil
-(string= "ab" "ABC")
- @result{} nil
address@hidden example
-
-The function @code{string=} ignores the text properties of the two
-strings. When @code{equal} (@pxref{Equality Predicates}) compares two
-strings, it uses @code{string=}.
-
-For technical reasons, a unibyte and a multibyte string are
address@hidden if and only if they contain the same sequence of
-character codes and all these codes are either in the range 0 through
-127 (@acronym{ASCII}) or 160 through 255 (@code{eight-bit-graphic}).
-However, when a unibyte string gets converted to a multibyte string,
-all characters with codes in the range 160 through 255 get converted
-to characters with higher codes, whereas @acronym{ASCII} characters
-remain unchanged. Thus, a unibyte string and its conversion to
-multibyte are only @code{equal} if the string is all @acronym{ASCII}.
-Character codes 160 through 255 are not entirely proper in multibyte
-text, even though they can occur. As a consequence, the situation
-where a unibyte and a multibyte string are @code{equal} without both
-being all @acronym{ASCII} is a technical oddity that very few Emacs
-Lisp programmers ever get confronted with. @xref{Text
-Representations}.
address@hidden defun
-
address@hidden string-equal string1 string2
address@hidden is another name for @code{string=}.
address@hidden defun
-
address@hidden lexical comparison
address@hidden string< string1 string2
address@hidden (findex string< causes problems for permuted index!!)
-This function compares two strings a character at a time. It
-scans both the strings at the same time to find the first pair of corresponding
-characters that do not match. If the lesser character of these two is
-the character from @var{string1}, then @var{string1} is less, and this
-function returns @code{t}. If the lesser character is the one from
address@hidden, then @var{string1} is greater, and this function returns
address@hidden If the two strings match entirely, the value is @code{nil}.
-
-Pairs of characters are compared according to their character codes.
-Keep in mind that lower case letters have higher numeric values in the
address@hidden character set than their upper case counterparts; digits and
-many punctuation characters have a lower numeric value than upper case
-letters. An @acronym{ASCII} character is less than any address@hidden
-character; a unibyte address@hidden character is always less than any
-multibyte address@hidden character (@pxref{Text Representations}).
-
address@hidden
address@hidden
-(string< "abc" "abd")
- @result{} t
-(string< "abd" "abc")
- @result{} nil
-(string< "123" "abc")
- @result{} t
address@hidden group
address@hidden example
-
-When the strings have different lengths, and they match up to the
-length of @var{string1}, then the result is @code{t}. If they match up
-to the length of @var{string2}, the result is @code{nil}. A string of
-no characters is less than any other string.
-
address@hidden
address@hidden
-(string< "" "abc")
- @result{} t
-(string< "ab" "abc")
- @result{} t
-(string< "abc" "")
- @result{} nil
-(string< "abc" "ab")
- @result{} nil
-(string< "" "")
- @result{} nil
address@hidden group
address@hidden example
-
-Symbols are also allowed as arguments, in which case their print names
-are used.
address@hidden defun
-
address@hidden string-lessp string1 string2
address@hidden is another name for @code{string<}.
address@hidden defun
-
address@hidden compare-strings string1 start1 end1 string2 start2 end2
&optional ignore-case
-This function compares the specified part of @var{string1} with the
-specified part of @var{string2}. The specified part of @var{string1}
-runs from index @var{start1} up to index @var{end1} (@code{nil} means
-the end of the string). The specified part of @var{string2} runs from
-index @var{start2} up to index @var{end2} (@code{nil} means the end of
-the string).
-
-The strings are both converted to multibyte for the comparison
-(@pxref{Text Representations}) so that a unibyte string and its
-conversion to multibyte are always regarded as equal. If
address@hidden is address@hidden, then case is ignored, so that
-upper case letters can be equal to lower case letters.
-
-If the specified portions of the two strings match, the value is
address@hidden Otherwise, the value is an integer which indicates how many
-leading characters agree, and which string is less. Its absolute value
-is one plus the number of characters that agree at the beginning of the
-two strings. The sign is negative if @var{string1} (or its specified
-portion) is less.
address@hidden defun
-
address@hidden assoc-string key alist &optional case-fold
-This function works like @code{assoc}, except that @var{key} must be a
-string or symbol, and comparison is done using @code{compare-strings}.
-Symbols are converted to strings before testing.
-If @var{case-fold} is address@hidden, it ignores case differences.
-Unlike @code{assoc}, this function can also match elements of the alist
-that are strings or symbols rather than conses. In particular, @var{alist} can
-be a list of strings or symbols rather than an actual alist.
address@hidden Lists}.
address@hidden defun
-
- See also the @code{compare-buffer-substrings} function in
address@hidden Text}, for a way to compare text in buffers. The
-function @code{string-match}, which matches a regular expression
-against a string, can be used for a kind of string comparison; see
address@hidden Search}.
-
address@hidden String Conversion
address@hidden node-name, next, previous, up
address@hidden Conversion of Characters and Strings
address@hidden conversion of strings
-
- This section describes functions for conversions between characters,
-strings and integers. @code{format} (@pxref{Formatting Strings})
-and @code{prin1-to-string}
-(@pxref{Output Functions}) can also convert Lisp objects into strings.
address@hidden (@pxref{Input Functions}) can ``convert'' a
-string representation of a Lisp object into an object. The functions
address@hidden and @code{string-make-unibyte} convert the
-text representation of a string (@pxref{Converting Representations}).
-
- @xref{Documentation}, for functions that produce textual descriptions
-of text characters and general input events
-(@code{single-key-description} and @code{text-char-description}). These
-are used primarily for making help messages.
-
address@hidden char-to-string character
address@hidden character to string
-This function returns a new string containing one character,
address@hidden This function is semi-obsolete because the function
address@hidden is more general. @xref{Creating Strings}.
address@hidden defun
-
address@hidden string-to-char string
address@hidden string to character
- This function returns the first character in @var{string}. If the
-string is empty, the function returns 0. The value is also 0 when the
-first character of @var{string} is the null character, @acronym{ASCII} code
-0.
-
address@hidden
-(string-to-char "ABC")
- @result{} 65
-
-(string-to-char "xyz")
- @result{} 120
-(string-to-char "")
- @result{} 0
address@hidden
-(string-to-char "\000")
- @result{} 0
address@hidden group
address@hidden example
-
-This function may be eliminated in the future if it does not seem useful
-enough to retain.
address@hidden defun
-
address@hidden number-to-string number
address@hidden integer to string
address@hidden integer to decimal
-This function returns a string consisting of the printed base-ten
-representation of @var{number}, which may be an integer or a floating
-point number. The returned value starts with a minus sign if the argument is
-negative.
-
address@hidden
-(number-to-string 256)
- @result{} "256"
address@hidden
-(number-to-string -23)
- @result{} "-23"
address@hidden group
-(number-to-string -23.5)
- @result{} "-23.5"
address@hidden example
-
address@hidden int-to-string
address@hidden is a semi-obsolete alias for this function.
-
-See also the function @code{format} in @ref{Formatting Strings}.
address@hidden defun
-
address@hidden string-to-number string &optional base
address@hidden string to number
-This function returns the numeric value of the characters in
address@hidden If @var{base} is address@hidden, it must be an integer
-between 2 and 16 (inclusive), and integers are converted in that base.
-If @var{base} is @code{nil}, then base ten is used. Floating point
-conversion only works in base ten; we have not implemented other
-radices for floating point numbers, because that would be much more
-work and does not seem useful. If @var{string} looks like an integer
-but its value is too large to fit into a Lisp integer,
address@hidden returns a floating point result.
-
-The parsing skips spaces and tabs at the beginning of @var{string},
-then reads as much of @var{string} as it can interpret as a number in
-the given base. (On some systems it ignores other whitespace at the
-beginning, not just spaces and tabs.) If the first character after
-the ignored whitespace is neither a digit in the given base, nor a
-plus or minus sign, nor the leading dot of a floating point number,
-this function returns 0.
-
address@hidden
-(string-to-number "256")
- @result{} 256
-(string-to-number "25 is a perfect square.")
- @result{} 25
-(string-to-number "X256")
- @result{} 0
-(string-to-number "-4.5")
- @result{} -4.5
-(string-to-number "1e5")
- @result{} 100000.0
address@hidden example
-
address@hidden string-to-int
address@hidden is an obsolete alias for this function.
address@hidden defun
-
- Here are some other functions that can convert to or from a string:
-
address@hidden @code
address@hidden concat
address@hidden can convert a vector or a list into a string.
address@hidden Strings}.
-
address@hidden vconcat
address@hidden can convert a string into a vector. @xref{Vector
-Functions}.
-
address@hidden append
address@hidden can convert a string into a list. @xref{Building Lists}.
address@hidden table
-
address@hidden Formatting Strings
address@hidden node-name, next, previous, up
address@hidden Formatting Strings
address@hidden formatting strings
address@hidden strings, formatting them
-
- @dfn{Formatting} means constructing a string by substitution of
-computed values at various places in a constant string. This constant string
-controls how the other values are printed, as well as where they appear;
-it is called a @dfn{format string}.
-
- Formatting is often useful for computing messages to be displayed. In
-fact, the functions @code{message} and @code{error} provide the same
-formatting feature described here; they differ from @code{format} only
-in how they use the result of formatting.
-
address@hidden format string &rest objects
-This function returns a new string that is made by copying
address@hidden and then replacing any format specification
-in the copy with encodings of the corresponding @var{objects}. The
-arguments @var{objects} are the computed values to be formatted.
-
-The characters in @var{string}, other than the format specifications,
-are copied directly into the output, including their text properties,
-if any.
address@hidden defun
-
address@hidden @samp{%} in format
address@hidden format specification
- A format specification is a sequence of characters beginning with a
address@hidden Thus, if there is a @samp{%d} in @var{string}, the
address@hidden function replaces it with the printed representation of
-one of the values to be formatted (one of the arguments @var{objects}).
-For example:
-
address@hidden
address@hidden
-(format "The value of fill-column is %d." fill-column)
- @result{} "The value of fill-column is 72."
address@hidden group
address@hidden example
-
- Since @code{format} interprets @samp{%} characters as format
-specifications, you should @emph{never} pass an arbitrary string as
-the first argument. This is particularly true when the string is
-generated by some Lisp code. Unless the string is @emph{known} to
-never include any @samp{%} characters, pass @code{"%s"}, described
-below, as the first argument, and the string as the second, like this:
-
address@hidden
- (format "%s" @var{arbitrary-string})
address@hidden example
-
- If @var{string} contains more than one format specification, the
-format specifications correspond to successive values from
address@hidden Thus, the first format specification in @var{string}
-uses the first such value, the second format specification uses the
-second such value, and so on. Any extra format specifications (those
-for which there are no corresponding values) cause an error. Any
-extra values to be formatted are ignored.
-
- Certain format specifications require values of particular types. If
-you supply a value that doesn't fit the requirements, an error is
-signaled.
-
- Here is a table of valid format specifications:
-
address@hidden @samp
address@hidden %s
-Replace the specification with the printed representation of the object,
-made without quoting (that is, using @code{princ}, not
address@hidden@pxref{Output Functions}). Thus, strings are represented
-by their contents alone, with no @samp{"} characters, and symbols appear
-without @samp{\} characters.
-
-If the object is a string, its text properties are
-copied into the output. The text properties of the @samp{%s} itself
-are also copied, but those of the object take priority.
-
address@hidden %S
-Replace the specification with the printed representation of the object,
-made with quoting (that is, using @address@hidden
-Functions}). Thus, strings are enclosed in @samp{"} characters, and
address@hidden characters appear where necessary before special characters.
-
address@hidden %o
address@hidden integer to octal
-Replace the specification with the base-eight representation of an
-integer.
-
address@hidden %d
-Replace the specification with the base-ten representation of an
-integer.
-
address@hidden %x
address@hidden %X
address@hidden integer to hexadecimal
-Replace the specification with the base-sixteen representation of an
-integer. @samp{%x} uses lower case and @samp{%X} uses upper case.
-
address@hidden %c
-Replace the specification with the character which is the value given.
-
address@hidden %e
-Replace the specification with the exponential notation for a floating
-point number.
-
address@hidden %f
-Replace the specification with the decimal-point notation for a floating
-point number.
-
address@hidden %g
-Replace the specification with notation for a floating point number,
-using either exponential notation or decimal-point notation, whichever
-is shorter.
-
address@hidden %%
-Replace the specification with a single @samp{%}. This format
-specification is unusual in that it does not use a value. For example,
address@hidden(format "%% %d" 30)} returns @code{"% 30"}.
address@hidden table
-
- Any other format character results in an @samp{Invalid format
-operation} error.
-
- Here are several examples:
-
address@hidden
address@hidden
-(format "The name of this buffer is %s." (buffer-name))
- @result{} "The name of this buffer is strings.texi."
-
-(format "The buffer object prints as %s." (current-buffer))
- @result{} "The buffer object prints as strings.texi."
-
-(format "The octal value of %d is %o,
- and the hex value is %x." 18 18 18)
- @result{} "The octal value of 18 is 22,
- and the hex value is 12."
address@hidden group
address@hidden example
-
address@hidden field width
address@hidden padding
- A specification can have a @dfn{width}, which is a signed decimal
-number between the @samp{%} and the specification character. If the
-printed representation of the object contains fewer characters than
-this width, @code{format} extends it with padding. The padding goes
-on the left if the width is positive (or starts with zero) and on the
-right if the width is negative. The padding character is normally a
-space, but it's @samp{0} if the width starts with a zero.
-
- Some of these conventions are ignored for specification characters
-for which they do not make sense. That is, @samp{%s}, @samp{%S} and
address@hidden accept a width starting with 0, but still pad with
address@hidden on the left. Also, @samp{%%} accepts a width, but
-ignores it. Here are some examples of padding:
-
address@hidden
-(format "%06d is padded on the left with zeros" 123)
- @result{} "000123 is padded on the left with zeros"
-
-(format "%-6d is padded on the right" 123)
- @result{} "123 is padded on the right"
address@hidden example
-
address@hidden
-If the width is too small, @code{format} does not truncate the
-object's printed representation. Thus, you can use a width to specify
-a minimum spacing between columns with no risk of losing information.
-
- In the following three examples, @samp{%7s} specifies a minimum
-width of 7. In the first case, the string inserted in place of
address@hidden has only 3 letters, it needs 4 blank spaces as padding. In
-the second case, the string @code{"specification"} is 13 letters wide
-but is not truncated. In the third case, the padding is on the right.
-
address@hidden
address@hidden
-(format "The word `%7s' actually has %d letters in it."
- "foo" (length "foo"))
- @result{} "The word ` foo' actually has 3 letters in it."
address@hidden group
-
address@hidden
-(format "The word `%7s' actually has %d letters in it."
- "specification" (length "specification"))
- @result{} "The word `specification' actually has 13 letters in it."
address@hidden group
-
address@hidden
-(format "The word `%-7s' actually has %d letters in it."
- "foo" (length "foo"))
- @result{} "The word `foo ' actually has 3 letters in it."
address@hidden group
address@hidden smallexample
-
address@hidden precision in format specifications
- All the specification characters allow an optional @dfn{precision}
-before the character (after the width, if present). The precision is
-a decimal-point @samp{.} followed by a digit-string. For the
-floating-point specifications (@samp{%e}, @samp{%f}, @samp{%g}), the
-precision specifies how many decimal places to show; if zero, the
-decimal-point itself is also omitted. For @samp{%s} and @samp{%S},
-the precision truncates the string to the given width, so @samp{%.3s}
-shows only the first three characters of the representation for
address@hidden Precision has no effect for other specification
-characters.
-
address@hidden flags in format specifications
- Immediately after the @samp{%} and before the optional width and
-precision, you can put certain ``flag'' characters.
-
- @samp{+} as a flag inserts a plus sign before a positive number, so
-that it always has a sign. A space character as flag inserts a space
-before a positive number. (Otherwise, positive numbers start with the
-first digit.) Either of these two flags ensures that positive numbers
-and negative numbers use the same number of columns. These flags are
-ignored except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}, and if
-both flags are used, the @samp{+} takes precedence.
-
- The flag @samp{#} specifies an ``alternate form'' which depends on
-the format in use. For @samp{%o} it ensures that the result begins
-with a @samp{0}. For @samp{%x} and @samp{%X}, it prefixes the result
-with @samp{0x} or @samp{0X}. For @samp{%e}, @samp{%f}, and @samp{%g},
-the @samp{#} flag means include a decimal point even if the precision
-is zero.
-
address@hidden Case Conversion
address@hidden node-name, next, previous, up
address@hidden Case Conversion in Lisp
address@hidden upper case
address@hidden lower case
address@hidden character case
address@hidden case conversion in Lisp
-
- The character case functions change the case of single characters or
-of the contents of strings. The functions normally convert only
-alphabetic characters (the letters @samp{A} through @samp{Z} and
address@hidden through @samp{z}, as well as address@hidden letters); other
-characters are not altered. You can specify a different case
-conversion mapping by specifying a case table (@pxref{Case Tables}).
-
- These functions do not modify the strings that are passed to them as
-arguments.
-
- The examples below use the characters @samp{X} and @samp{x} which have
address@hidden codes 88 and 120 respectively.
-
address@hidden downcase string-or-char
-This function converts a character or a string to lower case.
-
-When the argument to @code{downcase} is a string, the function creates
-and returns a new string in which each letter in the argument that is
-upper case is converted to lower case. When the argument to
address@hidden is a character, @code{downcase} returns the
-corresponding lower case character. This value is an integer. If the
-original character is lower case, or is not a letter, then the value
-equals the original character.
-
address@hidden
-(downcase "The cat in the hat")
- @result{} "the cat in the hat"
-
-(downcase ?X)
- @result{} 120
address@hidden example
address@hidden defun
-
address@hidden upcase string-or-char
-This function converts a character or a string to upper case.
-
-When the argument to @code{upcase} is a string, the function creates
-and returns a new string in which each letter in the argument that is
-lower case is converted to upper case.
-
-When the argument to @code{upcase} is a character, @code{upcase}
-returns the corresponding upper case character. This value is an integer.
-If the original character is upper case, or is not a letter, then the
-value returned equals the original character.
-
address@hidden
-(upcase "The cat in the hat")
- @result{} "THE CAT IN THE HAT"
-
-(upcase ?x)
- @result{} 88
address@hidden example
address@hidden defun
-
address@hidden capitalize string-or-char
address@hidden capitalization
-This function capitalizes strings or characters. If
address@hidden is a string, the function creates and returns a new
-string, whose contents are a copy of @var{string-or-char} in which each
-word has been capitalized. This means that the first character of each
-word is converted to upper case, and the rest are converted to lower
-case.
-
-The definition of a word is any sequence of consecutive characters that
-are assigned to the word constituent syntax class in the current syntax
-table (@pxref{Syntax Class Table}).
-
-When the argument to @code{capitalize} is a character, @code{capitalize}
-has the same result as @code{upcase}.
-
address@hidden
address@hidden
-(capitalize "The cat in the hat")
- @result{} "The Cat In The Hat"
address@hidden group
-
address@hidden
-(capitalize "THE 77TH-HATTED CAT")
- @result{} "The 77th-Hatted Cat"
address@hidden group
-
address@hidden
-(capitalize ?x)
- @result{} 88
address@hidden group
address@hidden example
address@hidden defun
-
address@hidden upcase-initials string-or-char
-If @var{string-or-char} is a string, this function capitalizes the
-initials of the words in @var{string-or-char}, without altering any
-letters other than the initials. It returns a new string whose
-contents are a copy of @var{string-or-char}, in which each word has
-had its initial letter converted to upper case.
-
-The definition of a word is any sequence of consecutive characters that
-are assigned to the word constituent syntax class in the current syntax
-table (@pxref{Syntax Class Table}).
-
-When the argument to @code{upcase-initials} is a character,
address@hidden has the same result as @code{upcase}.
-
address@hidden
address@hidden
-(upcase-initials "The CAT in the hAt")
- @result{} "The CAT In The HAt"
address@hidden group
address@hidden example
address@hidden defun
-
- @xref{Text Comparison}, for functions that compare strings; some of
-them ignore case differences, or can optionally ignore case differences.
-
address@hidden Case Tables
address@hidden The Case Table
-
- You can customize case conversion by installing a special @dfn{case
-table}. A case table specifies the mapping between upper case and lower
-case letters. It affects both the case conversion functions for Lisp
-objects (see the previous section) and those that apply to text in the
-buffer (@pxref{Case Changes}). Each buffer has a case table; there is
-also a standard case table which is used to initialize the case table
-of new buffers.
-
- A case table is a char-table (@pxref{Char-Tables}) whose subtype is
address@hidden This char-table maps each character into the
-corresponding lower case character. It has three extra slots, which
-hold related tables:
-
address@hidden @var
address@hidden upcase
-The upcase table maps each character into the corresponding upper
-case character.
address@hidden canonicalize
-The canonicalize table maps all of a set of case-related characters
-into a particular member of that set.
address@hidden equivalences
-The equivalences table maps each one of a set of case-related characters
-into the next character in that set.
address@hidden table
-
- In simple cases, all you need to specify is the mapping to lower-case;
-the three related tables will be calculated automatically from that one.
-
- For some languages, upper and lower case letters are not in one-to-one
-correspondence. There may be two different lower case letters with the
-same upper case equivalent. In these cases, you need to specify the
-maps for both lower case and upper case.
-
- The extra table @var{canonicalize} maps each character to a canonical
-equivalent; any two characters that are related by case-conversion have
-the same canonical equivalent character. For example, since @samp{a}
-and @samp{A} are related by case-conversion, they should have the same
-canonical equivalent character (which should be either @samp{a} for both
-of them, or @samp{A} for both of them).
-
- The extra table @var{equivalences} is a map that cyclically permutes
-each equivalence class (of characters with the same canonical
-equivalent). (For ordinary @acronym{ASCII}, this would map @samp{a} into
address@hidden and @samp{A} into @samp{a}, and likewise for each set of
-equivalent characters.)
-
- When you construct a case table, you can provide @code{nil} for
address@hidden; then Emacs fills in this slot from the lower case
-and upper case mappings. You can also provide @code{nil} for
address@hidden; then Emacs fills in this slot from
address@hidden In a case table that is actually in use, those
-components are address@hidden Do not try to specify @var{equivalences}
-without also specifying @var{canonicalize}.
-
- Here are the functions for working with case tables:
-
address@hidden case-table-p object
-This predicate returns address@hidden if @var{object} is a valid case
-table.
address@hidden defun
-
address@hidden set-standard-case-table table
-This function makes @var{table} the standard case table, so that it will
-be used in any buffers created subsequently.
address@hidden defun
-
address@hidden standard-case-table
-This returns the standard case table.
address@hidden defun
-
address@hidden current-case-table
-This function returns the current buffer's case table.
address@hidden defun
-
address@hidden set-case-table table
-This sets the current buffer's case table to @var{table}.
address@hidden defun
-
address@hidden with-case-table table address@hidden
-The @code{with-case-table} macro saves the current case table, makes
address@hidden the current case table, evaluates the @var{body} forms,
-and finally restores the case table. The return value is the value of
-the last form in @var{body}. The case table is restored even in case
-of an abnormal exit via @code{throw} or error (@pxref{Nonlocal
-Exits}).
address@hidden defmac
-
- Some language environments may modify the case conversions of
address@hidden characters; for example, in the Turkish language
-environment, the @acronym{ASCII} character @samp{I} is downcased into
-a Turkish ``dotless i''. This can interfere with code that requires
-ordinary ASCII case conversion, such as implementations of
address@hidden network protocols. In that case, use the
address@hidden macro with the variable @var{ascii-case-table},
-which stores the unmodified case table for the @acronym{ASCII}
-character set.
-
address@hidden ascii-case-table
-The case table for the @acronym{ASCII} character set. This should not be
-modified by any language environment settings.
address@hidden defvar
-
- The following three functions are convenient subroutines for packages
-that define address@hidden character sets. They modify the specified
-case table @var{case-table}; they also modify the standard syntax table.
address@hidden Tables}. Normally you would use these functions to change
-the standard case table.
-
address@hidden set-case-syntax-pair uc lc case-table
-This function specifies a pair of corresponding letters, one upper case
-and one lower case.
address@hidden defun
-
address@hidden set-case-syntax-delims l r case-table
-This function makes characters @var{l} and @var{r} a matching pair of
-case-invariant delimiters.
address@hidden defun
-
address@hidden set-case-syntax char syntax case-table
-This function makes @var{char} case-invariant, with syntax
address@hidden
address@hidden defun
-
address@hidden Command describe-buffer-case-table
-This command displays a description of the contents of the current
-buffer's case table.
address@hidden deffn
-
address@hidden
- arch-tag: 700b8e95-7aa5-4b52-9eb3-8f2e1ea152b4
address@hidden ignore
- [Emacs-diffs] Changes to strings.texi,
Glenn Morris <=