Part of the Programming glossary:

In object-oriented programming, polymorphism (from the Greek meaning "having multiple forms") is the characteristic of being able to assign a different meaning or usage to something in different contexts - specifically, to allow an entity such as a variable, a function, or an object to have more than one form. There are several different kinds of polymorphism.

1) A variable with a given name may be allowed to have different forms and the program can determine which form of the variable to use at the time of execution. For example, a variable named USERID may be capable of being either an integer (whole number) or a string of characters (perhaps because the programmer wants to allow a user to enter a user ID as either an employee number - an integer - or with a name - a string of characters). By giving the program a way to distinguish which form is being handled in each case, either kind can be recognized and handled.

2) A named function can also vary depending on the parameters it is given. For example, if given a variable that is an integer, the function chosen would be to seek a match against a list of employee numbers; if the variable were a string, it would seek a match against a list of names. In either case, both functions would be known in the program by the same name. This type of polymorphism is sometimes known as overloading.

In C++, for example, the operator known as the plus sign (+) - which is effectively a simple named function - can be assigned to operate on two objects such that it adds them together (perhaps the most common form of the + operation) or, as in boolean searching, a + can indicate a logical "and" (meaning that both words separated by the + operator must be present in order for a citation to be returned). In another context, the + sign could mean an operation to concatenate the two objects or strings of letters on either side of the + sign.

A given operator can also be given yet another meaning when combined with another operator. For example, in the C++ language, a "++" following a variable can mean "increment this value by 1". The meaning of a particular operator is defined as part of a class definition. Since the programmer can create classes, the programmer can also define how operators work for this class of objects; in effect, the programmer can redefine the computing language.

3) Polymorphism can mean, as in the ML language, a data type of "any," such that when specified for a list, a list containing any data types can be processed by a function. (For example, if a function simply determines the length of a list, it doesn't matter what data types are in the list.)

4) In PHP, polymorphism means that if B is a descendant of A and a function can accept A as a parameter, it can also accept B.

This was last updated in April 2005
Contributor(s): Jack Ulsh
Posted by: Margaret Rouse

Related Terms

Definitions

  • Java Champion

    - The Java Champion designation is awarded to leaders and visionaries in the Java technology community. (SearchSOA.com)

  • application program interface (API)

    - An application program interface (API) is code that allows two software programs to communicate with each other. Typically, APIs are released for third-party development as part of a software devel... (SearchExchange.com)

  • algorithm

    - An algorithm (pronounced AL-go-rith-um) is a procedure or formula for solving a problem. (WhatIs.com)

Glossaries

  • Programming

    - Terms related to software programming, including definitions about programming languages and words and phrases about software design, coding, testing and debugging.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question. Find an Answer.Powered by ITKnowledgeExchange.com

Ask An IT Question

Get answers from your peers on your most technical challenges

Ask Question

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.