From 5b83dc2e909fb512b8458cf5b196df06e728b040 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Thu, 19 Apr 2012 16:41:44 -0700
Subject: [PATCH] sequences.extras: adding slice-when (non-destructive
 split-when).

---
 extra/sequences/extras/extras-tests.factor | 6 +++++-
 extra/sequences/extras/extras.factor       | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/extra/sequences/extras/extras-tests.factor b/extra/sequences/extras/extras-tests.factor
index 45f08db319..968f827997 100644
--- a/extra/sequences/extras/extras-tests.factor
+++ b/extra/sequences/extras/extras-tests.factor
@@ -1,4 +1,5 @@
-USING: ascii kernel make math sequences sequences.extras tools.test ;
+USING: ascii kernel make math sequences sequences.extras strings
+tools.test ;
 
 IN: sequences.extras.tests
 
@@ -45,3 +46,6 @@ IN: sequences.extras.tests
 
 { " a b c d e " }
 [ " a      b  c   d    e   " [ blank? ] " " collapse ] unit-test
+
+{ { "hello," " " "world!" " " " " } }
+[ "hello, world!  " [ blank? ] slice-when [ >string ] map ] unit-test
diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index 10a743e868..eac2f5236a 100644
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -95,3 +95,11 @@ IN: sequences.extras
     [ [ first empty? ] dip [ prepend ] curry when ]
     [ [ last empty? ] dip [ append ] curry when ]
     2tri ; inline
+
+:: slice-when ( seq quot: ( elt -- ? ) -- seq' )
+    seq length :> len
+    0 [ len dupd < ] [
+        dup seq quot find-from drop
+        [ 2dup = [ 1 + ] when ] [ len ] if*
+        [ seq <slice> ] keep len or swap
+    ] produce nip ; inline