1;;; pmatch, a simple matcher 2 3;;; Copyright (C) 2009, 2010, 2012 Free Software Foundation, Inc 4;;; Copyright (C) 2005,2006,2007 Oleg Kiselyov 5;;; Copyright (C) 2007 Daniel P. Friedman 6;;; 7;;; This library is free software; you can redistribute it and/or 8;;; modify it under the terms of the GNU Lesser General Public 9;;; License as published by the Free Software Foundation; either 10;;; version 3 of the License, or (at your option) any later version. 11;;; 12;;; This library is distributed in the hope that it will be useful, 13;;; but WITHOUT ANY WARRANTY; without even the implied warranty of 14;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15;;; Lesser General Public License for more details. 16;;; 17;;; You should have received a copy of the GNU Lesser General Public 18;;; License along with this library; if not, write to the Free Software 19;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 21;;; Originally written by Oleg Kiselyov for LeanTAP in Kanren, which is 22;;; available under the MIT license. 23;;; 24;;; http://kanren.cvs.sourceforge.net/viewvc/kanren/kanren/mini/leanTAP.scm?view=log 25;;; 26;;; This version taken from: 27;;; αKanren: A Fresh Name in Nominal Logic Programming 28;;; by William E. Byrd and Daniel P. Friedman 29;;; Proceedings of the 2007 Workshop on Scheme and Functional Programming 30;;; Université Laval Technical Report DIUL-RT-0701 31 32;;; To be clear: the original code is MIT-licensed, and the modifications 33;;; made to it by Guile are under Guile's license (currently LGPL v3+). 34 35;;; Code: 36 37(define-module (system base pmatch) 38 #:export-syntax (pmatch)) 39 40(define-syntax-rule (pmatch e cs ...) 41 (let ((v e)) (pmatch1 v cs ...))) 42 43(define-syntax pmatch1 44 (syntax-rules (else guard) 45 ((_ v) (if #f #f)) 46 ((_ v (else e0 e ...)) (let () e0 e ...)) 47 ((_ v (pat (guard g ...) e0 e ...) cs ...) 48 (let ((fk (lambda () (pmatch1 v cs ...)))) 49 (ppat v pat 50 (if (and g ...) (let () e0 e ...) (fk)) 51 (fk)))) 52 ((_ v (pat e0 e ...) cs ...) 53 (let ((fk (lambda () (pmatch1 v cs ...)))) 54 (ppat v pat (let () e0 e ...) (fk)))))) 55 56(define-syntax ppat 57 (syntax-rules (_ quote unquote) 58 ((_ v _ kt kf) kt) 59 ((_ v () kt kf) (if (null? v) kt kf)) 60 ((_ v (quote lit) kt kf) 61 (if (equal? v (quote lit)) kt kf)) 62 ((_ v (unquote var) kt kf) (let ((var v)) kt)) 63 ((_ v (x . y) kt kf) 64 (if (pair? v) 65 (let ((vx (car v)) (vy (cdr v))) 66 (ppat vx x (ppat vy y kt kf) kf)) 67 kf)) 68 ((_ v lit kt kf) (if (eq? v (quote lit)) kt kf)))) 69