Editing Generic function (section)

== In Common Lisp Object System ==
In some systems for [[object-oriented programming]] such as the [[Common Lisp Object System]] (CLOS)<ref>[http://www.dreamsongs.com/Files/ECOOP.pdf The Common Lisp Object System: An Overview]</ref> and [[Dylan (programming language)|Dylan]], a ''generic function'' is an entity made up of all methods having the same name. Typically a ''generic function'' is an instance of a class that [[Inheritance (object-oriented programming)|inherits]] both from ''function'' and ''standard-object''. Thus generic functions are both functions (that can be called with and applied to arguments) and ordinary objects. The book ''[[The Art of the Metaobject Protocol]]'' explains the implementation and use of CLOS generic functions in detail.

One of the early object-oriented programming extensions to Lisp is [[Flavors (programming language)|Flavors]]. It used the usual message sending paradigm influenced by [[Smalltalk]]. The Flavors syntax to send a message is:

<syntaxhighlight lang="lisp">
 (send object :message)
</syntaxhighlight>

With New Flavors, it was decided the message should be a real function and the usual function calling syntax should be used:

<syntaxhighlight lang="lisp">
 (message object)
</syntaxhighlight>

''message'' now is a ''generic function'', an object and function in its own right. Individual implementations of the ''message'' are called ''methods''.

The same idea was implemented in [[CommonLoops]].<ref>{{Cite web |url=http://www2.parc.com/istl/groups/gir/papers/stefik-commonloops-oopsla66.pdf |title=CommonLoops, Merging Lisp and Object-Oriented Programming |access-date=2009-12-10 |archive-url=https://web.archive.org/web/20110604013117/http://www2.parc.com/istl/groups/gir/papers/stefik-commonloops-oopsla66.pdf |archive-date=2011-06-04 |url-status=dead }}</ref> New Flavors and CommonLoops were the main influence for the Common Lisp Object System.