if-empty changes

[factor.git] / extra / inverse / inverse.factor

diff --git a/extra/inverse/inverse.factor b/extra/inverse/inverse.factor
index c7925b94bed4b86a57e5c8724294bbbd9eee72e1..b843c73983d6adafb616fef992dee8bc98ec9a7f 100755 (executable)
--- a/extra/inverse/inverse.factor
+++ b/extra/inverse/inverse.factor
@@ -34,9 +34,8 @@ M: no-inverse summary
     drop "The word cannot be used in pattern matching" ;
 
 : next ( revquot -- revquot* first )
-    dup empty?
     [ "Badly formed math inverse" throw ]
-    [ unclip-slice ] if ;
+    [ unclip-slice ] if-empty ;
 
 : constant-word? ( word -- ? )
     stack-effect
@@ -116,8 +115,7 @@ M: pop-inverse inverse
     "pop-inverse" word-prop compose call ;
 
 : (undo) ( revquot -- )
-    dup empty? [ drop ]
-    [ unclip-slice inverse % (undo) ] if ;
+    [ unclip-slice inverse % (undo) ] unless-empty ;
 
 : [undo] ( quot -- undo )
     flatten fold reverse [ (undo) ] [ ] make ;