From 3123654a8462634914010b5135261cc4237f9661 Mon Sep 17 00:00:00 2001
From: Chris Double <chris@bethia.(none)>
Date: Sat, 5 Apr 2008 18:05:09 +1300
Subject: [PATCH] Refactor optional peg parser

---
 extra/peg/peg.factor | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/extra/peg/peg.factor b/extra/peg/peg.factor
index 8c427d5e27..332f7164f8 100755
--- a/extra/peg/peg.factor
+++ b/extra/peg/peg.factor
@@ -380,17 +380,15 @@ M: repeat1-parser (compile) ( parser -- quot )
   ] ; 
 
 TUPLE: optional-parser p1 ;
-MATCH-VARS: ?quot ;
 
-: optional-pattern ( -- quot )
-  [
-    ?quot [ input-slice f <parse-result> ] unless* 
-  ] ;
+: check-optional ( result -- result )
+  [ input-slice f <parse-result> ] unless* ;
 
 M: optional-parser (compile) ( parser -- quot )
-  p1>> compiled-parser \ ?quot optional-pattern match-replace ;
+  p1>> compiled-parser 1quotation '[ @ check-optional ] ;
 
 TUPLE: semantic-parser p1 quot ;
+MATCH-VARS: ?quot ;
 
 MATCH-VARS: ?parser ;