[cl-unification-cvs] CVS cl-unification

[mantoniotti]

Update of /project/cl-unification/cvsroot/cl-unification
In directory cl-net:/tmp/cvs-serv18479

Modified Files:
	match-block.lisp 
Log Message:
Added MATCHF* macros.


--- /project/cl-unification/cvsroot/cl-unification/match-block.lisp	2009/04/15 10:16:24	1.9
+++ /project/cl-unification/cvsroot/cl-unification/match-block.lisp	2009/12/17 16:41:38	1.10
@@ -303,6 +303,68 @@
          (let ((,object-var ,object))
            ,(generate-matchers non-otherwise-clauses))))))
 
+
+(defmacro matchf-case ((object &key errorp default-substitution match-case-named)
+                      &rest clauses)
+  "MATCHF-CASE sets up a CASE-like environment for multiple template matching clauses.
+
+The syntax of MATCHF-CASE comprises a number of clauses of the form
+
+  <clause> ::= <regular-clause> | <default-clause>
+  <regular-clause> ::= (<template> &body <forms>)
+  <default-clause> ::= (t &body <forms>)
+                   |   (otherwise &body <forms>)
+<form> and <forms> are regular Common Lisp forms.
+<template> is a unification template.
+
+The full syntax of MATCHF-CASE is
+
+  matchf-case <object> (&key errorp default-substitution) <clauses>
+
+Each clause evaluates its forms in an environment where the variables
+present in the template are bound lexically.  Note that both variable
+names '?FOO' and 'FOO' are bound for convenience.
+
+The values returned by the MATCH-CASE form are those of the last form in
+the first clause that satisfies the match test.
+
+If ERRORP is non-NIL then if none of the regular clauses matches, then
+an error of type UNIFICATION-NON-EXAUSTIVE is signalled, regardless of
+any default clause.  Otherwise, the default clause behaves as a
+standard CASE default clause.  The default value of ERRORP is NIL.
+
+MATCHF-CASE behaves like MATCH-CASE, but the patterns are not
+evaluated (i.e., it relies on MATCHF instead of MATCH to construct the
+macro expansion.
+"
+  (declare (ignore default-substitution)) ; For the time being.
+  (let* ((object-var (gensym "OBJECT-VAR-"))
+         (otherwise-clause-present-p
+          (member (caar (last clauses)) '(t otherwise)))
+	 (non-otherwise-clauses
+          (if otherwise-clause-present-p
+              (butlast clauses)
+              clauses))
+	 (otherwise-clause
+          (if otherwise-clause-present-p
+              (first (last clauses))
+              (when errorp
+                `(t (error 'unification-non-exhaustive
+                           :format-control "Non exhaustive matching.")))))
+         )
+    (labels ((generate-matchers (clauses)
+	       (if (null clauses)
+		   `(progn ,@(rest otherwise-clause))
+		   (destructuring-bind (pattern &rest body)
+		       (car clauses)
+		     `(handler-case (matchf (,pattern ,object-var)
+				      , at body)
+		        (unification-failure ()
+			  ,(generate-matchers (cdr clauses))))))))
+      `(block ,match-case-named
+         (let ((,object-var ,object))
+           ,(generate-matchers non-otherwise-clauses))))))
+
 ;;;;---------------------------------------------------------------------------
 ;;;; Testing.