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