Re: Defining polymorphism vs. overloading

Here is my favorite so far:


> - Overloading is the ability to have the same name (symbol) attached
> to different entities (functions, procedures, variables or whatsoever).
>
> - Polymorphism is the ability to have the compiler decide *at runtime*
> which entity to use depending on the runtime type (class or whatever)
> of the contents of variables.
>
> - Generic code is a chunk of code that has the ability of performing
> the same algorithm with more than one type. The actual types may be
> known at runtime (as in Smalltalk) or at compile time (as in Ada).
> . . .
> Joaquim Manuel Soares Baptista, aka px@fctunl.rccn.pt, px@unl.uucp


However, I would revise the definition of polymorphism as follows:


- Polymorphism is the ability to have a single entity (usually a parameter or
a pointer) refer to objects/values of more than one type. Run-time
polymorphism (like C++) allows the dispatch to type-specific code to be made
at run-time. Compile-time polymorphism (like Ada's generics) performs the
"dispatch" to type-specific code at compile-time.


- Generic code is code that manipulates polymorphic parameters/pointers, by
taking advantage of the commonality across the multiple types represented by
them. In most cases, however, it must eventually "dispatch" to type-specific
code.


S. Tucker Taft stt@inmet.inmet.com; uunet!inmet!stt
Intermetrics, Inc.
Cambridge, MA 02138
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