combinators.extras: adding keepd.

diff --git a/extra/combinators/extras/extras-tests.factor b/extra/combinators/extras/extras-tests.factor
index 594ec44c461dde7e4f89f867f7e51018b44a08eb..71b773ef99848cb3b3ef340cc186aa73c8eb43ed 100644 (file)
--- a/extra/combinators/extras/extras-tests.factor
+++ b/extra/combinators/extras/extras-tests.factor
@@ -27,3 +27,5 @@ IN: combinators.extras.tests
 { 2 15 } [ 1 2 3 4 5 6 [ - - ] [ + + ] 3bi* ] unit-test
 
 { 2 5 } [ 1 2 3 4 5 6 [ - - ] 3bi@ ] unit-test
+
+{ 3 1 } [ 1 2 [ + ] keepd ] unit-test

diff --git a/extra/combinators/extras/extras.factor b/extra/combinators/extras/extras.factor
index 28a87ef608a317513aebed1766869794819aeec3..dffd402aa1477af0b1df4829d409080aeefffeef 100644 (file)
--- a/extra/combinators/extras/extras.factor
+++ b/extra/combinators/extras/extras.factor
@@ -24,3 +24,6 @@ MACRO: cleave-array ( quots -- )
 
 : 3bi@ ( u v w x y z quot -- )
     dup 3bi* ; inline
+
+: keepd ( ..a x y quot: ( ..a x y -- ..b ) -- ..b x )
+    2keep drop ; inline