if-empty changes

[factor.git] / extra / backtrack / backtrack.factor

diff --git a/extra/backtrack/backtrack.factor b/extra/backtrack/backtrack.factor
index db2c50173c9f8c85c7585fb448d4e9e5bf4bb9f9..df397025f60f9399971fb1efcc1a60a8b5afce9e 100755 (executable)
--- a/extra/backtrack/backtrack.factor
+++ b/extra/backtrack/backtrack.factor
@@ -50,9 +50,8 @@ PRIVATE>
     [ amb-integer ] [ nth ] bi ;\r
 \r
 : amb ( seq -- elt )\r
-    dup empty?\r
-    [ drop fail f ]\r
-    [ unsafe-amb ] if ; inline\r
+    [ fail f ]\r
+    [ unsafe-amb ] if-empty ; inline\r
 \r
 MACRO: amb-execute ( seq -- quot )\r
     [ length 1 - ] [ <enum> [ 1quotation ] assoc-map ] bi\r