;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile ;;;; written by Michael Livshin ;;;; ;;;; 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))