Add guards to the match syntax.

I'm not sure the syntax is great, but it's very helpful to have.

1 files changed, 10 insertions, 1 deletions

diff --git a/match.csc b/match.csc
index 07ca98c..d188349 100644
--- a/match.csc
+++ b/match.csc
@@ -40,10 +40,19 @@
 
 
     (define-syntax match
-      (syntax-rules ()
+      (syntax-rules (when)
+        ((match x (pattern (when condition) result result* ...))
+         (if (and (matches? x pattern)
+                  condition)
+           (bind-pattern x pattern result result* ...)))
         ((match x (pattern result1 result2 ...))
          (if (matches? x pattern)
            (bind-pattern x pattern result1 result2 ...)))
+        ((match x (pattern (when condition) result result* ...) clause clause* ...)
+         (if (and (matches? x pattern)
+                  condition)
+           (bind-pattern x pattern result result* ...)
+           (match x clause clause* ...)))
         ((match x (pattern result1 result2 ...) clause1 clause2 ...)
          (if (matches? x pattern)
            (bind-pattern x pattern result1 result2 ...)