Support pmatch from Guile.

* module/mes/pmatch.scm: New file.
* module/mes/pmatch.mes: New file.
* AUTHORS: Mention it.

AUTHORS

@@ -26,6 +26,9 @@ module/mes/psyntax.pp [generated]
 Optargs from Guile
 module/mes/optargs.scm
 
+Pmatch from Guile
+module/mes/pmatch.scm
+
 Srfi-1 bits from Guile
 module/srfi/srfi-1.scm
 

module/mes/pmatch.mes

@@ -0,0 +1,27 @@
+;;; -*-scheme-*-
+
+;;; Mes --- Maxwell Equations of Software
+;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;;
+;;; This file is part of Mes.
+;;;
+;;; Mes 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 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; Mes 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 Mes.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(mes-use-module (mes guile))
+(mes-use-module (mes quasiquote))
+(include-from-path "mes/pmatch.scm")

module/mes/pmatch.scm

@@ -0,0 +1,68 @@
+;;; pmatch, a simple matcher
+
+;;; Copyright (C) 2009, 2010, 2012 Free Software Foundation, Inc
+;;; Copyright (C) 2005,2006,2007 Oleg Kiselyov
+;;; Copyright (C) 2007 Daniel P. Friedman
+;;;
+;;; 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 3 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+;;; Originally written by Oleg Kiselyov for LeanTAP in Kanren, which is
+;;; available under the MIT license.
+;;;
+;;; http://kanren.cvs.sourceforge.net/viewvc/kanren/kanren/mini/leanTAP.scm?view=log
+;;;
+;;; This version taken from:
+;;; αKanren: A Fresh Name in Nominal Logic Programming
+;;; by William E. Byrd and Daniel P. Friedman
+;;; Proceedings of the 2007 Workshop on Scheme and Functional Programming
+;;; Université Laval Technical Report DIUL-RT-0701
+
+;;; To be clear: the original code is MIT-licensed, and the modifications
+;;; made to it by Guile are under Guile's license (currently LGPL v3+).
+
+;;; Code:
+
+(define-module (system base pmatch)
+  #:export-syntax (pmatch))
+
+(define-syntax-rule (pmatch e cs ...)
+  (let ((v e)) (pmatch1 v cs ...)))
+
+(define-syntax pmatch1
+  (syntax-rules (else guard)
+    ((_ v) (if #f #f))
+    ((_ v (else e0 e ...)) (let () e0 e ...))
+    ((_ v (pat (guard g ...) e0 e ...) cs ...)
+     (let ((fk (lambda () (pmatch1 v cs ...))))
+       (ppat v pat
+             (if (and g ...) (let () e0 e ...) (fk))
+             (fk))))
+    ((_ v (pat e0 e ...) cs ...)
+     (let ((fk (lambda () (pmatch1 v cs ...))))
+       (ppat v pat (let () e0 e ...) (fk))))))
+
+(define-syntax ppat
+  (syntax-rules (_ quote unquote)
+    ((_ v _ kt kf) kt)
+    ((_ v () kt kf) (if (null? v) kt kf))
+    ((_ v (quote lit) kt kf)
+     (if (equal? v (quote lit)) kt kf))
+    ((_ v (unquote var) kt kf) (let ((var v)) kt))
+    ((_ v (x . y) kt kf)
+     (if (pair? v)
+         (let ((vx (car v)) (vy (cdr v)))
+           (ppat vx x (ppat vy y kt kf) kf))
+         kf))
+    ((_ v lit kt kf) (if (eq? v (quote lit)) kt kf))))