X-Git-Url: https://gitweb.factorcode.org/gitweb.cgi?p=factor.git;a=blobdiff_plain;f=extra%2Fsequences%2Fextras%2Fextras.factor;h=027a3af19969716904c232efaf834c26190bfbdf;hp=f47ebc56508934065d8e4552fe9df11cd3efa84e;hb=cdf7cce0463bea3ea406c7ef5bcac72991413326;hpb=ae305990c566b5986e634140835d3c27b08c8af3

diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index f47ebc5650..027a3af199 100644
--- 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
+
+: nth-index ( n obj seq -- i )
+    [ = dup [ drop 1 - dup 0 < ] when ] with find drop nip ;