#| -*-Scheme-*-

$Id$

Copyright 2006 Massachusetts Institute of Technology

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 of the License, 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 program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Equality constraints make two connectors hold the same values.

(declare (usual-integrations))

(define cp:B=A
  (cp:make-constraint-type 'B=A '(b a)
    (lambda (constraint)
      (let ((b (cp:get-connector constraint 'b))
	    (a (cp:get-connector constraint 'a)))
	(cond ((cp:has-value? a)
	       (cp:set-value b (cp:value-of a) (list a) constraint))
	      ((cp:has-value? b)
	       (cp:set-value a (cp:value-of b) (list b) constraint)))))))