present: add a ``M\\ callable present``

core/present/present.factor

@@ -1,7 +1,7 @@
 ! Copyright (C) 2008, 2009 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors effects io.pathnames kernel math math.parser
-sequences strings vocabs words ;
+quotations sequences strings vocabs words ;
 IN: present
 
 GENERIC: present ( object -- string )
@@ -27,3 +27,10 @@ M: effect present effect>string ;
 M: f present drop "" ;
 
 M: pathname present string>> ;
+
+M: callable present
+    [ "[ ]" ] [
+        [ drop "[ " ]
+        [ [ present ] map " " join ]
+        [ drop " ]" ] tri 3append
+    ] if-empty ;