matcher: add :match parameter macro.

With this, we can do matching anywhere we are able to specify
a function parameter list and a body, and we can specify
ordinary arguments, which are inserted to the left of the
implicit match. Plus, it specialy integrates with :key.

* lisplib.c (match_set_entries): Autoload on :match.

* share/txr/stdlib/match.tl (:match): New parameter macro.

* txr.1: Documented.

1 files changed, 13 insertions, 0 deletions

diff --git a/share/txr/stdlib/match.tl b/share/txr/stdlib/match.tl
index e2a55256..8932cc71 100644
--- a/share/txr/stdlib/match.tl
+++ b/share/txr/stdlib/match.tl
@@ -678,6 +678,19 @@
   (tree-bind (lambda args . body) (expand-lambda-match clauses)
     ^(defun ,name ,args . ,body)))
 
+(define-param-expander :match (params clauses menv form)
+  (unless (proper-list-p params)
+    (compile-error form "~s is incompatible with dotted parameter lists" :match))
+  (when (find : params)
+    (compile-error form "~s is incompatible with optional parameters" :match))
+  (tree-bind (lambda lparams . body) (expand-lambda-match clauses)
+    (let ((dashdash (member '-- params)))
+      (cons (append (ldiff params dashdash)
+                    (butlastn 0 lparams)
+                    dashdash
+                    (nthlast 0 lparams))
+            body))))
+
 (defun non-triv-pat-p (syntax) t)
 
 (defun non-triv-pat-p (syntax)