[bpt/guile.git] / ice-9 / and-let-star.scm

;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile
;;;; written by Michael Livshin <mike@olan.com>
;;;;
;;;; 	Copyright (C) 1999, 2001 Free Software Foundation, Inc.
;;;; 
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2, or (at your option)
;;;; any later version.
;;;; 
;;;; This program 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 General Public License for more details.
;;;; 
;;;; You should have received a copy of the GNU General Public License
;;;; along with this software; see the file COPYING.  If not, write to
;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
;;;; Boston, MA 02111-1307 USA
;;;;
;;;; As a special exception, the Free Software Foundation gives permission
;;;; for additional uses of the text contained in its release of GUILE.
;;;;
;;;; The exception is that, if you link the GUILE library with other files
;;;; to produce an executable, this does not by itself cause the
;;;; resulting executable to be covered by the GNU General Public License.
;;;; Your use of that executable is in no way restricted on account of
;;;; linking the GUILE library code into it.
;;;;
;;;; This exception does not however invalidate any other reasons why
;;;; the executable file might be covered by the GNU General Public License.
;;;;
;;;; This exception applies only to the code released by the
;;;; Free Software Foundation under the name GUILE.  If you copy
;;;; code from other Free Software Foundation releases into a copy of
;;;; GUILE, as the General Public License permits, the exception does
;;;; not apply to the code that you add in this way.  To avoid misleading
;;;; anyone as to the status of such modified files, you must delete
;;;; this exception notice from them.
;;;;
;;;; If you write modifications of your own for GUILE, it is your choice
;;;; whether to permit this exception to apply to your modifications.
;;;; If you do not wish that, delete this exception notice.

(define-module (ice-9 and-let-star)
  :export-syntax (and-let*))

(defmacro and-let* (vars . body)

  (define (expand vars body)
    (cond
     ((null? vars)
      `(begin ,@body))
     ((pair? vars)
      (let ((exp (car vars)))
        (cond
         ((pair? exp)
          (cond
           ((null? (cdr exp))
            `(and ,(car exp) ,(expand (cdr vars) body)))
           (else
            (let ((var (car exp))
                  (val (cadr exp)))
              `(let (,exp)
                 (and ,var ,(expand (cdr vars) body)))))))
         (else
          `(and ,exp ,(expand (cdr vars) body))))))
     (else
      (error "not a proper list" vars))))

  (expand vars body))
Commit	Line	Data
93a6e9c4 MV	1	;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile
	2	;;;; written by Michael Livshin <mike@olan.com>
	3	;;;;
e39bbe80	4	;;;; Copyright (C) 1999, 2001 Free Software Foundation, Inc.
93a6e9c4 MV	5	;;;;
	6	;;;; This program is free software; you can redistribute it and/or modify
	7	;;;; it under the terms of the GNU General Public License as published by
	8	;;;; the Free Software Foundation; either version 2, or (at your option)
	9	;;;; any later version.
	10	;;;;
	11	;;;; This program is distributed in the hope that it will be useful,
	12	;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	;;;; GNU General Public License for more details.
	15	;;;;
	16	;;;; You should have received a copy of the GNU General Public License
	17	;;;; along with this software; see the file COPYING. If not, write to
	18	;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
	19	;;;; Boston, MA 02111-1307 USA
a482f2cc MV	20	;;;;
	21	;;;; As a special exception, the Free Software Foundation gives permission
	22	;;;; for additional uses of the text contained in its release of GUILE.
	23	;;;;
	24	;;;; The exception is that, if you link the GUILE library with other files
	25	;;;; to produce an executable, this does not by itself cause the
	26	;;;; resulting executable to be covered by the GNU General Public License.
	27	;;;; Your use of that executable is in no way restricted on account of
	28	;;;; linking the GUILE library code into it.
	29	;;;;
	30	;;;; This exception does not however invalidate any other reasons why
	31	;;;; the executable file might be covered by the GNU General Public License.
	32	;;;;
	33	;;;; This exception applies only to the code released by the
	34	;;;; Free Software Foundation under the name GUILE. If you copy
	35	;;;; code from other Free Software Foundation releases into a copy of
	36	;;;; GUILE, as the General Public License permits, the exception does
	37	;;;; not apply to the code that you add in this way. To avoid misleading
	38	;;;; anyone as to the status of such modified files, you must delete
	39	;;;; this exception notice from them.
	40	;;;;
	41	;;;; If you write modifications of your own for GUILE, it is your choice
	42	;;;; whether to permit this exception to apply to your modifications.
	43	;;;; If you do not wish that, delete this exception notice.
93a6e9c4	44
1a179b03 MD	45	(define-module (ice-9 and-let-star)
1a179b03 MD	46	:export-syntax (and-let*))
93a6e9c4 MV	47
	48	(defmacro and-let* (vars . body)
	49
	50	(define (expand vars body)
	51	(cond
	52	((null? vars)
	53	`(begin ,@body))
	54	((pair? vars)
	55	(let ((exp (car vars)))
	56	(cond
	57	((pair? exp)
	58	(cond
	59	((null? (cdr exp))
	60	`(and ,(car exp) ,(expand (cdr vars) body)))
	61	(else
	62	(let ((var (car exp))
	63	(val (cadr exp)))
	64	`(let (,exp)
	65	(and ,var ,(expand (cdr vars) body)))))))
	66	(else
	67	`(and ,exp ,(expand (cdr vars) body))))))
	68	(else
	69	(error "not a proper list" vars))))
	70
	71	(expand vars body))