sequences.extras: Allow from to be f in ?<slice>

diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index 1d9148dd2791f850b88bf21f68c8d4da1ab2d908..b057f6e4c208acaee5ceaf5a8ecc6bd28cf94b30 100644 (file)
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -149,8 +149,10 @@ PRIVATE>
 : cut-slice* ( seq n -- before after )
     [ head-slice* ] [ tail-slice* ] 2bi ;
 
-: ?<slice> ( from to/f sequence -- slice )
-    over [ nip [ length ] [ ] bi ] unless <slice> ; inline
+: ?<slice> ( from/f to/f sequence -- slice )
+    [ [ 0 ] unless* ] 2dip
+    over [ nip [ length ] [ ] bi ] unless
+    <slice> ; inline
 
 : sequence>slice ( sequence -- slice )
     [ drop 0 ] [ length ] [ ] tri <slice> ; inline