Polymorphic Procedures
A procedure that has multiple type signatures is called polymorphic. In the case of operators, the use of the same operator with different types is called overloading.
| + : | integer X integer &rarr integer |
| + : | real X real &rarr real |
Polymorphic procedures are often found in object-oriented programming:
(defmethod move-to ((self drawable-object)
(x integer) (y integer))
(send self 'erase)
(send self 'set-pos x y)
(send self 'draw) )