Re: Polymorphism vs. Overloading

Gabriela O. de Vivo <gdevivo@conicit.ve> wrote:


>Last week I was invited to join a Thesis (MsC) presentation.
>At some point a question raised about the exact difference between
>Polymorphism and Overloading.


I just learned this in class from Professor Borgida (borgida@cs.rutgers.edu):


Types of polymorphism:


o Ad-hoc/overloading: One function name can be associated with several bodies,
    distinguished by the type of arguments passed to the function (and sometimes
    the type of the result). [c++, CLU, Ada, Pascal I/O, {+, -, * /} in
    {ML, C, FORTRAN}]. It is resolved completely at compile time. Example:
    put(0); put("hello"); put(1.0); calls three different "put" procedures.


o Parametric polymorphism/"genericity": Same source code generates multiple
    copies of object code, one for each instance. [\-calculus: /\t, ML, CLU,
    Ada generics, c++ templates]. Examples: generic linked lists, generic sort.


o Subtype polymorphism: Same run-time code operates on different types.
    (The types all partially share the same representation). [Smalltalk/c++ class
    heirarchy, range subtypes in pascal/Ada, derived types in Ada]. Example:
    Operations of type PERSON being applied to an object of type STUDENT.




                                                                regards,
                                                                joe


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