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Re: Functional record "setters", a different approach
From: |
Mark H Weaver |
Subject: |
Re: Functional record "setters", a different approach |
Date: |
Wed, 11 Apr 2012 04:20:54 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.92 (gnu/linux) |
I wrote:
> I rushed out my last email because I didn't want anyone else to waste
> time working on the same functionality.
More importantly, I just realized that the patch I sent out included
only part of my changes. It was missing my initial work to clean up the
srfi-9 code before I started adding the new functionality. Here's the
complete patch. Apologies for the wasted bandwidth :-(
Mark
diff --git a/module/srfi/srfi-9.scm b/module/srfi/srfi-9.scm
index da71d1e..866d28b 100644
--- a/module/srfi/srfi-9.scm
+++ b/module/srfi/srfi-9.scm
@@ -29,8 +29,8 @@
;; <predicate name>
;; <field spec> ...)
;;
-;; <field spec> -> (<field tag> <accessor name>)
-;; -> (<field tag> <accessor name> <modifier name>)
+;; <field spec> -> (<field tag> <getter name>)
+;; -> (<field tag> <getter name> <setter name>)
;;
;; <field tag> -> <identifier>
;; <... name> -> <identifier>
@@ -60,7 +60,7 @@
(define-module (srfi srfi-9)
#:use-module (srfi srfi-1)
- #:export (define-record-type))
+ #:export-syntax (define-record-type))
(cond-expand-provide (current-module) '(srfi-9))
@@ -68,8 +68,26 @@
;; because the public one has a different `make-procedure-name', so
;; using it would require users to recompile code that uses SRFI-9. See
;; <http://lists.gnu.org/archive/html/guile-devel/2011-04/msg00111.html>.
+;;
+
+(define-syntax-rule (define-inlinable (name formals ...) body ...)
+ (define-tagged-inlinable () (name formals ...) body ...))
+
+;; 'define-tagged-inlinable' has an additional feature: it stores a map
+;; of keys to values that can be retrieved at expansion time. This is
+;; currently used to retrieve the rtd id, field index, and record copier
+;; macro for an arbitrary getter.
+
+(define %%type #f) ; a private syntax literal
+(define-syntax-rule (getter-type getter) (getter () %%type))
-(define-syntax define-inlinable
+(define %%index #f) ; a private syntax literal
+(define-syntax-rule (getter-index getter) (getter () %%index))
+
+(define %%copier #f) ; a private syntax literal
+(define-syntax-rule (getter-copier getter) (getter () %%copier))
+
+(define-syntax define-tagged-inlinable
(lambda (x)
(define (make-procedure-name name)
(datum->syntax name
@@ -77,7 +95,7 @@
'-procedure)))
(syntax-case x ()
- ((_ (name formals ...) body ...)
+ ((_ ((key value) ...) (name formals ...) body ...)
(identifier? #'name)
(with-syntax ((proc-name (make-procedure-name #'name))
((args ...) (generate-temporaries #'(formals ...))))
@@ -86,7 +104,8 @@
body ...)
(define-syntax name
(lambda (x)
- (syntax-case x ()
+ (syntax-case x (key ...)
+ ((_ () key) #'value) ...
((_ args ...)
#'((lambda (formals ...)
body ...)
@@ -109,90 +128,139 @@
(loop (cdr fields) (+ 1 off)))))
(display ">" p))
+(define (throw-bad-struct s who)
+ (throw 'wrong-type-arg who
+ "Wrong type argument: ~S" (list s)
+ (list s)))
+
+(define (make-copier-id type-name)
+ (datum->syntax type-name
+ (symbol-append '%% (syntax->datum type-name)
+ '-modified-copy)))
+
+(define-syntax %%modified-copy
+ (lambda (x)
+ (syntax-case x ()
+ ((_ type-name (getter-id ...) check? s (getter expr) ...)
+ (every identifier? #'(getter ...))
+ (let ((copier-name (syntax->datum (make-copier-id #'type-name)))
+ (getter+exprs #'((getter expr) ...)))
+ (define (lookup id default-expr)
+ (let ((results
+ (filter (lambda (g+e)
+ (free-identifier=? id (car g+e)))
+ getter+exprs)))
+ (case (length results)
+ ((0) default-expr)
+ ((1) (cadar results))
+ (else (syntax-violation
+ copier-name "duplicate getter" x id)))))
+ (for-each (lambda (id)
+ (or (find (lambda (getter-id)
+ (free-identifier=? id getter-id))
+ #'(getter-id ...))
+ (syntax-violation
+ copier-name "unknown getter" x id)))
+ #'(getter ...))
+ (with-syntax ((unsafe-expr
+ #`(make-struct
+ type-name 0
+ #,@(map (lambda (getter index)
+ (lookup getter #`(struct-ref s #,index)))
+ #'(getter-id ...)
+ (iota (length #'(getter-id ...)))))))
+ (if (syntax->datum #'check?)
+ #`(if (eq? (struct-vtable s) type-name)
+ unsafe-expr
+ (throw-bad-struct
+ s '#,(datum->syntax #'here copier-name)))
+ #'unsafe-expr)))))))
+
(define-syntax define-record-type
(lambda (x)
(define (field-identifiers field-specs)
- (syntax-case field-specs ()
- (()
- '())
- ((field-spec)
- (syntax-case #'field-spec ()
- ((name accessor) #'(name))
- ((name accessor modifier) #'(name))))
- ((field-spec rest ...)
- (append (field-identifiers #'(field-spec))
- (field-identifiers #'(rest ...))))))
-
- (define (field-indices fields)
- (fold (lambda (field result)
- (let ((i (if (null? result)
- 0
- (+ 1 (cdar result)))))
- (alist-cons field i result)))
- '()
- fields))
-
- (define (constructor type-name constructor-spec indices)
+ (map (lambda (field-spec)
+ (syntax-case field-spec ()
+ ((name getter) #'name)
+ ((name getter setter) #'name)))
+ field-specs))
+
+ (define (getter-identifiers field-specs)
+ (map (lambda (field-spec)
+ (syntax-case field-spec ()
+ ((name getter) #'getter)
+ ((name getter setter) #'getter)))
+ field-specs))
+
+ (define (constructor form type-name constructor-spec field-names)
(syntax-case constructor-spec ()
((ctor field ...)
- (let ((field-count (length indices))
- (ctor-args (map (lambda (field)
- (cons (syntax->datum field) field))
- #'(field ...))))
+ (every identifier? #'(field ...))
+ (let ((ctor-args (map (lambda (field)
+ (let ((name (syntax->datum field)))
+ (or (memq name field-names)
+ (syntax-violation
+ 'define-record-type
+ "unknown field in constructor-spec"
+ form field))
+ (cons name field)))
+ #'(field ...))))
#`(define-inlinable #,constructor-spec
(make-struct #,type-name 0
- #,@(unfold
- (lambda (field-num)
- (>= field-num field-count))
- (lambda (field-num)
- (let* ((name
- (car (find (lambda (f+i)
- (= (cdr f+i) field-num))
- indices)))
- (arg (assq name ctor-args)))
- (if (pair? arg)
- (cdr arg)
- #'#f)))
- 1+
- 0)))))))
-
- (define (accessors type-name field-specs indices)
- (syntax-case field-specs ()
- (()
- #'())
- ((field-spec)
- (syntax-case #'field-spec ()
- ((name accessor)
- (with-syntax ((index (assoc-ref indices (syntax->datum #'name))))
- #`((define-inlinable (accessor s)
- (if (eq? (struct-vtable s) #,type-name)
- (struct-ref s index)
- (throw 'wrong-type-arg 'accessor
- "Wrong type argument: ~S" (list s)
- (list s)))))))
- ((name accessor modifier)
- (with-syntax ((index (assoc-ref indices (syntax->datum #'name))))
- #`(#,@(accessors type-name #'((name accessor)) indices)
- (define-inlinable (modifier s val)
- (if (eq? (struct-vtable s) #,type-name)
- (struct-set! s index val)
- (throw 'wrong-type-arg 'modifier
- "Wrong type argument: ~S" (list s)
- (list s)))))))))
- ((field-spec rest ...)
- #`(#,@(accessors type-name #'(field-spec) indices)
- #,@(accessors type-name #'(rest ...) indices)))))
+ #,@(map (lambda (name)
+ (assq-ref ctor-args name))
+ field-names)))))))
+
+ (define (copier type-name getter-ids copier-id)
+ (with-syntax ((type-name type-name)
+ (getter-ids getter-ids)
+ ;; FIXME: Using 'copier-id' here (without stripping
+ ;; its wrap) fails when 'define-record-type' is used
+ ;; at non-top-level. Why?
+ (copier-id (datum->syntax
+ #'here (syntax->datum copier-id))))
+ #'(define-syntax-rule
+ (copier-id check? s (getter expr) (... ...))
+ (%%modified-copy type-name getter-ids
+ check? s (getter expr) (... ...)))))
+
+ (define (getters type-name getter-ids copier-id)
+ (map (lambda (getter index)
+ #`(define-tagged-inlinable
+ ((%%type #,type-name)
+ (%%index #,index)
+ (%%copier #,copier-id))
+ (#,getter s)
+ (if (eq? (struct-vtable s) #,type-name)
+ (struct-ref s #,index)
+ (throw-bad-struct s '#,getter))))
+ getter-ids
+ (iota (length getter-ids))))
+
+ (define (setters type-name field-specs)
+ (filter-map (lambda (field-spec index)
+ (syntax-case field-spec ()
+ ((name getter) #f)
+ ((name getter setter)
+ #`(define-inlinable (setter s val)
+ (if (eq? (struct-vtable s) #,type-name)
+ (struct-set! s #,index val)
+ (throw-bad-struct s 'setter))))))
+ field-specs
+ (iota (length field-specs))))
(syntax-case x ()
((_ type-name constructor-spec predicate-name field-spec ...)
- (let* ((fields (field-identifiers #'(field-spec ...)))
- (field-count (length fields))
+ (let* ((field-ids (field-identifiers #'(field-spec ...)))
+ (getter-ids (getter-identifiers #'(field-spec ...)))
+ (field-count (length field-ids))
(layout (string-concatenate (make-list field-count "pw")))
- (indices (field-indices (map syntax->datum fields)))
+ (field-names (map syntax->datum field-ids))
(ctor-name (syntax-case #'constructor-spec ()
- ((ctor args ...) #'ctor))))
+ ((ctor args ...) #'ctor)))
+ (copier-id (make-copier-id #'type-name)))
#`(begin
- #,(constructor #'type-name #'constructor-spec indices)
+ #,(constructor x #'type-name #'constructor-spec field-names)
(define type-name
(let ((rtd (make-struct/no-tail
@@ -200,7 +268,7 @@
'#,(datum->syntax #'here (make-struct-layout
layout))
default-record-printer
'type-name
- '#,fields)))
+ '#,field-ids)))
(set-struct-vtable-name! rtd 'type-name)
(struct-set! rtd (+ 2 vtable-offset-user) #,ctor-name)
rtd))
@@ -209,6 +277,9 @@
(and (struct? obj)
(eq? (struct-vtable obj) type-name)))
- #,@(accessors #'type-name #'(field-spec ...) indices)))))))
+ #,@(getters #'type-name getter-ids copier-id)
+ #,@(setters #'type-name #'(field-spec ...))
+ #,(copier #'type-name getter-ids copier-id)
+ ))))))
;;; srfi-9.scm ends here
diff --git a/module/srfi/srfi-9/gnu.scm b/module/srfi/srfi-9/gnu.scm
index 30c101b..d9c24a1 100644
--- a/module/srfi/srfi-9/gnu.scm
+++ b/module/srfi/srfi-9/gnu.scm
@@ -1,6 +1,6 @@
;;; Extensions to SRFI-9
-;; Copyright (C) 2010 Free Software Foundation, Inc.
+;; Copyright (C) 2010, 2012 Free Software Foundation, Inc.
;;
;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
@@ -23,8 +23,63 @@
;;; Code:
(define-module (srfi srfi-9 gnu)
- #:export (set-record-type-printer!))
+ #:use-module (srfi srfi-1)
+ #:export (set-record-type-printer!)
+ #:export-syntax (modified-copy modified-copy-nocheck))
(define (set-record-type-printer! type thunk)
"Set a custom printer THUNK for TYPE."
(struct-set! type vtable-index-printer thunk))
+
+(define-syntax-rule (modified-copy s . rest)
+ (%modified-copy #t s . rest))
+
+(define-syntax-rule (modified-copy-nocheck s . rest)
+ (%modified-copy #f s . rest))
+
+(define-syntax %modified-copy
+ (lambda (x)
+ (with-syntax ((getter-type #'(@@ (srfi srfi-9) getter-type))
+ (getter-index #'(@@ (srfi srfi-9) getter-index))
+ (getter-copier #'(@@ (srfi srfi-9) getter-copier)))
+ (syntax-case x ()
+ ((_ check? s)
+ #'s)
+ ((_ check? s (() e))
+ #'e)
+ ((_ check? struct-expr ((getter . rest) expr) ...)
+ ;;
+ ;; FIXME: Improve compile-time error reporting:
+ ;; 1. report an error if any getter-path is a
+ ;; prefix of any other getter-path.
+ ;; 2. report an error if the initial getters
+ ;; do not all belong to the same record type.
+ ;;
+ ;; forest : (tree ...)
+ ;; tree : (getter (rest . expr) ...)
+ (let ((forest
+ (fold (lambda (g r e forest)
+ (cond ((find (lambda (tree)
+ (free-identifier=? g (car tree)))
+ forest)
+ => (lambda (tree)
+ (cons (cons g (cons (cons r e)
+ (cdr tree)))
+ (delq tree forest))))
+ (else (cons (list g (cons r e))
+ forest))))
+ '()
+ #'(getter ...)
+ #'(rest ...)
+ #'(expr ...))))
+ #`(let ((s struct-expr))
+ ((getter-copier #,(caar forest))
+ check?
+ s
+ #,@(map (lambda (tree)
+ (with-syntax (((getter (rest . expr) ...) tree))
+ #'(getter (%modified-copy
+ check?
+ (struct-ref s (getter-index getter))
+ (rest expr) ...))))
+ forest)))))))))
diff --git a/test-suite/tests/srfi-9.test b/test-suite/tests/srfi-9.test
index 321fe16..d0668db 100644
--- a/test-suite/tests/srfi-9.test
+++ b/test-suite/tests/srfi-9.test
@@ -29,7 +29,7 @@
(x get-x) (y get-y set-y!))
(define-record-type :bar (make-bar i j) bar?
- (i get-i) (i get-j set-j!))
+ (i get-i) (j get-j set-j!))
(define f (make-foo 1))
(set-y! f 2)
- Functional record "setters", a different approach, Mark H Weaver, 2012/04/11
- Re: Functional record "setters", a different approach, Mark H Weaver, 2012/04/11
- Re: Functional record "setters", a different approach,
Mark H Weaver <=
- Re: Functional record "setters", a different approach, Ludovic Courtès, 2012/04/11
- Re: Functional record "setters", a different approach, Mark H Weaver, 2012/04/12
- Re: Functional record "setters", a different approach, Thien-Thi Nguyen, 2012/04/12
- Re: Functional record "setters", a different approach, Ludovic Courtès, 2012/04/12
- Re: Functional record "setters", a different approach, Mark H Weaver, 2012/04/12
- Re: Functional record "setters", a different approach, Ludovic Courtès, 2012/04/13
- Re: Functional record "setters", a different approach, Mark H Weaver, 2012/04/13