[cl-unification-cvs] CVS cl-unification

[mantoniotti]

Update of /project/cl-unification/cvsroot/cl-unification
In directory clnet:/tmp/cvs-serv31810

Added Files:
	apply-substitution.lisp 
Log Message:
See previous message.



--- /project/cl-unification/cvsroot/cl-unification/apply-substitution.lisp	2007/05/21 12:33:05	NONE
+++ /project/cl-unification/cvsroot/cl-unification/apply-substitution.lisp	2007/05/21 12:33:05	1.1
;;; -*- Mode: Lisp -*-

;;; substitutions.lisp
;;; General CL structures unifier.
;;; Substitution definitions.

(in-package "CL.EXT.DACF.UNIFICATION") ; DACF = Data And Control Flow.

;;;---------------------------------------------------------------------------
;;; Substitution application.

(defgeneric apply-substitution (substitution item))


(defmethod apply-substitution ((substitution environment) (s symbol))
  (cond ((variable-any-p s) s)
        ((variablep s)
         (multiple-value-bind (val foundp)
             (find-variable-value s substitution)
           (cond (foundp val)
                 (t (warn "~S is a free variable in the current environment." s)
                    s))))
        (t s)))


(defmethod apply-substitution ((substitution environment) (l cons))
  (cons (apply-substitution substitution (first l))
        (apply-substitution substitution (rest l))))

(defmethod apply-substitution ((substitution environment) (l null))
  '())

(export '(apply-substitution))


(defun ground-term (term &optional (substitution (make-empty-environment)))
  (apply-substitution substitution term))


;;; end of file -- apply-substitutions.lisp --