multi-arrows: arrows with multiple inputs

extra/models/arrow/multi/multi.factor

@@ -0,0 +1,11 @@
+! Copyright (C) 2009 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: models.arrow models.product stack-checker accessors fry
+generalizations kernel ;
+IN: models.arrow.multi
+
+: <n-arrow> ( quot int -- arrow )
+    [ narray <product> ] [ '[ _ firstn @ ] <arrow> ] bi ; inline
+
+: <2arrow> ( a b quot -- arrow ) 2 <n-arrow> ;
+: <3arrow> ( a b c quot -- arrow ) 3 <n-arrow> ;