sequences.extras: adding nth-index

[factor.git] / extra / sequences / extras / extras.factor

diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index f47ebc56508934065d8e4552fe9df11cd3efa84e..027a3af19969716904c232efaf834c26190bfbdf 100644 (file)
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -823,3 +823,6 @@ M: virtual-zip-index nth-unsafe
     over [ seq>> nth-unsafe ] [ 2array ] bi* ; inline
 
 INSTANCE: virtual-zip-index immutable-sequence
     over [ seq>> nth-unsafe ] [ 2array ] bi* ; inline
 
 INSTANCE: virtual-zip-index immutable-sequence

+
+: nth-index ( n obj seq -- i )
+    [ = dup [ drop 1 - dup 0 < ] when ] with find drop nip ;