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;;; srfi-9.scm --- define-record-type
;; Copyright (C) 2001, 2002, 2006, 2009, 2010, 2011 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
;; License as published by the Free Software Foundation; either
;; version 3 of the License, or (at your option) any later version.
;;
;; This library is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;; Lesser General Public License for more details.
;;
;; You should have received a copy of the GNU Lesser General Public
;; License along with this library; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;; Commentary:
;; This module exports the syntactic form `define-record-type', which
;; is the means for creating record types defined in SRFI-9.
;;
;; The syntax of a record type definition is:
;;
;; <record type definition>
;; -> (define-record-type <type name>
;; (<constructor name> <field tag> ...)
;; <predicate name>
;; <field spec> ...)
;;
;; <field spec> -> (<field tag> <accessor name>)
;; -> (<field tag> <accessor name> <modifier name>)
;;
;; <field tag> -> <identifier>
;; <... name> -> <identifier>
;;
;; Usage example:
;;
;; guile> (use-modules (srfi srfi-9))
;; guile> (define-record-type :foo (make-foo x) foo?
;; (x get-x) (y get-y set-y!))
;; guile> (define f (make-foo 1))
;; guile> f
;; #<:foo x: 1 y: #f>
;; guile> (get-x f)
;; 1
;; guile> (set-y! f 2)
;; 2
;; guile> (get-y f)
;; 2
;; guile> f
;; #<:foo x: 1 y: 2>
;; guile> (foo? f)
;; #t
;; guile> (foo? 1)
;; #f
;;; Code:
(define-module (srfi srfi-9)
#:use-module (srfi srfi-1)
#:export (define-record-type))
(cond-expand-provide (current-module) '(srfi-9))
;; Roll our own instead of using the public `define-inlinable'. This is
;; 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 define-inlinable
(lambda (x)
(define (make-procedure-name name)
(datum->syntax name
(symbol-append '% (syntax->datum name)
'-procedure)))
(syntax-case x ()
((_ (name formals ...) body ...)
(identifier? #'name)
(with-syntax ((proc-name (make-procedure-name #'name))
((args ...) (generate-temporaries #'(formals ...))))
#`(begin
(define (proc-name formals ...)
body ...)
(define-syntax name
(lambda (x)
(syntax-case x ()
((_ args ...)
#'((lambda (formals ...)
body ...)
args ...))
(_
(identifier? x)
#'proc-name))))))))))
(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)
(syntax-case constructor-spec ()
((ctor field ...)
(let ((field-count (length indices))
(ctor-args (map (lambda (field)
(cons (syntax->datum field) 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)))))
(syntax-case x ()
((_ type-name constructor-spec predicate-name field-spec ...)
(let* ((fields (field-identifiers #'(field-spec ...)))
(field-count (length fields))
(layout (string-concatenate (make-list field-count "pw")))
(indices (field-indices (map syntax->datum fields))))
#`(begin
(define type-name
(make-vtable #,layout
(lambda (obj port)
(format port "#<~A" 'type-name)
#,@(map (lambda (field)
(let* ((f (syntax->datum field))
(i (assoc-ref indices f)))
#`(format port " ~A: ~S" '#,field
(struct-ref obj #,i))))
fields)
(format port ">"))))
(define-inlinable (predicate-name obj)
(and (struct? obj)
(eq? (struct-vtable obj) type-name)))
#,(constructor #'type-name #'constructor-spec indices)
#,@(accessors #'type-name #'(field-spec ...) indices)))))))
;;; srfi-9.scm ends here
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