Editing Parameter (computer programming) (section)

=== Default arguments ===
Some programming languages such as [[Ada (programming language)|Ada]], [[C++]], [[Clojure]],{{Citation needed|date=June 2021}} [[Common Lisp]],<ref>{{Cite web|title=Functions|url=https://gigamonkeys.com/book/functions.html|access-date=2021-06-02|website=gigamonkeys.com}}</ref> [[Fortran 90]],<ref>{{Cite web|title=optional arguments|url=http://www.netlib.org/ccm/page/api/optional.html|access-date=2021-06-02|website=www.netlib.org}}</ref> [[Python (programming language)|Python]], [[Ruby (programming language)|Ruby]], [[Tcl (programming language)|Tcl]], and [[Windows PowerShell]]{{Citation needed|date=June 2021}} allow for a [[default argument]] to be explicitly or implicitly given in a subroutine's declaration. This allows the caller to omit that argument when calling the subroutine. If the default argument is explicitly given, then that value is used if it is not provided by the caller. If the default argument is implicit (sometimes by using a keyword such as ''Optional'') then the language provides a well-known value (such as ''[[Null pointer|null]]'', ''Empty'', zero, an empty string, etc.) if a value is not provided by the caller.

PowerShell example:
<syntaxhighlight lang="powershell">
function doc($g = 1.21) {
    "$g gigawatts? $g gigawatts? Great Scott!"
}
</syntaxhighlight>
<syntaxhighlight lang="ps1con">
PS  > doc
1.21 gigawatts? 1.21 gigawatts? Great Scott!

PS  > doc 88
88 gigawatts? 88 gigawatts? Great Scott!
</syntaxhighlight>
Default arguments can be seen as a special case of the variable-length argument list.