Adding lappend

extra/lists/lists-tests.factor

@@ -64,3 +64,7 @@ IN: lists.tests
 { { 3 4 { 5 6 { 7 } } } } [
   { 1 2 { 3 4 { 5 } } } seq>cons [ atom? ] [ 2 + ] traverse cons>seq
 ] unit-test
+    
+{ { 1 2 3 4 5 6 } } [
+    { 1 2 3 } seq>list { 4 5 6 } seq>list lappend list>seq
+] unit-test

extra/lists/lists.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2008 Chris Double & James Cash
+! Copyright (C) 2008 James Cash
 ! See http://factorcode.org/license.txt for BSD license.
 USING: kernel sequences accessors math arrays vectors classes words locals ;
 
@@ -75,6 +75,9 @@ M: object nil? drop f ;
 : lreverse ( list -- newlist )    
     nil [ swap cons ] foldl ;
     
+: lappend ( list1 list2 -- newlist )    
+    [ lreverse ] dip [ swap cons ] foldl ;
+    
 : seq>list ( seq -- list )    
     <reversed> nil [ swap cons ] reduce ;