Consize

% (c) Dominikus Herzberg, 2012 -- Creative Commons Lizenz CC BY-NC-SA 3.0
% Generic words demonstrating object-oriented dispatch in Consize

: def-generic+ ( wrd [ effect ] [ dispatch ] -- )
  [ { :else [ _|_ ] } case ] concat def+ ;

: def-generic ( wrd [ dispatch ] -- ) [ ??? ] swap def-generic+ ;

: def-method ( wrd val quot -- )
  swap rot
  [ lookup reverse pop top assoc ] keep
  [ lookup reverse top swap ] keep
  [ lookup reverse pop pop swapu swapu reverse ] keep
  swap def ;

\ ndrop [ dup ] def-generic
\ ndrop 0 [ drop ] def-method
\ ndrop :else [ swap drop 1 - ndrop ] def-method

[ x y ] [ x y z 1 ndrop ] unit-test
[ x   ] [ x y z 2 ndrop ] unit-test
[     ] [ x y z u v 5 ndrop ] unit-test

\ fact [ dup 0 == ] def-generic
\ fact true  [ drop 1 ] def-method
\ fact false [ dup 1 - fact * ] def-method

[ ( 1 1 2 6 24 120 720 ) ] [ [ 0 1 2 3 4 5 6 ] [ fact ] map ] unit-test