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Rob Browning 2004-06-20 14:19:59 +00:00
parent 8638c417b2
commit e96f5a6efd
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srfi/srfi-31.scm Normal file
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;;; srfi-34.scm --- Time/Date Library
;; Copyright (C) 2004 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 2.1 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
;;; Original author: Rob Browning <rlb@defaultvalue.org>
(define-module (srfi srfi-31)
:export-syntax (rec))
(define-macro (rec arg-form . body)
(cond
((and (symbol? arg-form) (= 1 (length body)))
;; (rec S (cons 1 (delay S)))
`(letrec ((,arg-form ,(car body)))
,arg-form))
;; (rec (f x) (+ x 1))
((list? arg-form)
`(letrec ((,(car arg-form) (lambda ,(cdr arg-form) ,@body)))
,(car arg-form)))
(else "syntax error in rec form" `(rec ,arg-form ,@body))))