sequences.extras: add count-head and count-tail

2017-09-28 22:41:21 -05:00 · 2017-09-28 22:41:21 -05:00 · 5a8f9284ab
parent 577d4618ca
commit 5a8f9284ab
1 changed files with 7 additions and 0 deletions
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@ -620,3 +620,10 @@ PRIVATE>
 : drop-while ( ... seq quot: ( ... elt -- ... ? ) -- tail-slice )
    [ '[ @ not ] find drop ] 2keep drop swap
    [ dup length ] unless* tail-slice ; inline
+
+: count-head ( seq quot -- n )
+    [ not ] compose find drop ; inline
+
+: count-tail ( seq quot -- n )
+    [ not ] compose [ find-last drop ] 2keep drop
+    length swap [ - 1 - ] when* ; inline