Local variable: Difference between revisions

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==Static local variables==

A special type of local variable, called a ''static local,'' is available in many mainstream languages (including [[C (programming language)|C]]/[[C++]], [[Visual Basic]], and [[Visual Basic (.NET)|VB.NET]] and [[PHP]]) which allows a value to be retained from one call of the function to another – it is a [[static variable]] with local scope. In this case, recursive calls to the function also have access to the (single, [[static memory allocation|statically allocated]]) variable. In all of the above languages, static variables are declared as such with a special ''storage class'' keyword (e.g., <code>static</code>).

Static locals in global functions have the same lifetime as [[static global variable]]s, because their value remains in memory for the life of the program,<ref>{{cite web|url= http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf |title=Current C standard }}&nbsp;{{small|(3.61&nbsp;MB)}} ({{As of|2009|lc=on}}). In particular, see section 6.2.4 “Storage durations of objects”, page 32.</ref> but have [[function scope]] (not global scope), as with automatic local variables.

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==Local variables in Perl==

[[Perl]] supports both dynamic and lexically-scoped local variables. The keyword <code>local</code> is used to define local dynamically-scoped variables, while <code>my</code> is used for local lexically-scoped variables. Since dynamic scoping is less common today, the Perl documentation warns that "<code>local</code> isn't what most people think of as “local”.".<ref>[http://perldoc.perl.org/functions/local.html perldoc.perl.org: local]</ref> Instead, the <code>local</code> keyword gives a temporary, [[scope (programmingcomputer science)|dynamically-scoped]] value to a global (package) variable, which lasts until the end of the enclosing block. However, the variable is visible to any function called from within the block.<ref>[http://perldoc.perl.org/perlsub.html#Temporary-Values-via-local() perldoc.perl.org: perlsub: Temporary Values via <code>local()</code>]</ref> To create lexically-scoped local variables, use the <code>my</code> operator instead.<ref>[http://perldoc.perl.org/perlsub.html#Private-Variables-via-my() perldoc.perl.org: perlsub: Private Variables via <code>my()</code>]</ref>

To understand how it works consider the following code: