From 159dd697e4726298e17058a70ac46f9608335e5b Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Fri, 30 Nov 2007 20:23:27 -0600
Subject: [PATCH] Fix stack effects Add take-while

---
 extra/sequences/lib/lib-tests.factor |  1 +
 extra/sequences/lib/lib.factor       | 10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/extra/sequences/lib/lib-tests.factor b/extra/sequences/lib/lib-tests.factor
index e1257748b3..82e2b911c3 100644
--- a/extra/sequences/lib/lib-tests.factor
+++ b/extra/sequences/lib/lib-tests.factor
@@ -41,3 +41,4 @@ math.functions tools.test ;
 [ V{ } [ delete-random drop ] keep length ] unit-test-fails
 
 [ { 1 9 25 } ] [ { 1 3 5 6 } [ sq ] [ even? ] map-until ] unit-test
+[ { 2 4 } ] [ { 2 4 1 3 } [ even? ] take-while ] unit-test
diff --git a/extra/sequences/lib/lib.factor b/extra/sequences/lib/lib.factor
index 0de90b74d6..e090feffea 100644
--- a/extra/sequences/lib/lib.factor
+++ b/extra/sequences/lib/lib.factor
@@ -63,10 +63,14 @@ IN: sequences.lib
 : delete-random ( seq -- value )
     [ length random ] keep [ nth ] 2keep delete-nth ;
 
-: (map-until) ( quot pred -- )
+: (map-until) ( quot pred -- quot )
     [ dup ] swap 3compose
     [ [ drop t ] [ , f ] if ] compose [ find 2drop ] curry ;
 
-: map-until ( seq quot pred -- )
-    #! Example: { 1 3 5 6 } [ sq ] [ even? ] map-until . -> { 1 9 25 }
+: map-until ( seq quot pred -- newseq )
     (map-until) { } make ;
+
+: take-while ( seq quot -- newseq )
+    [ not ] compose
+    [ find drop [ head-slice ] when* ] curry
+    [ dup ] swap compose keep like ;