Automatic variable: Difference between revisions

Revision as of 21:27, 25 July 2020

Revision as of 21:30, 9 January 2021

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(Called ''local variables''.)

Similar to C and C++, but there is no <code>auto</code> or <code>register</code> keyword. However, the Java compiler will not allow the usage of a not-explicitly-initialized local variable and will give a compilation error (unlike C and C++ where the compiler will usually only give a warning). The Java standard demands that every local variable must be explicitly initialized before being used.<ref>{{cite web | url=http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#4.12.5 | title=4.12.5 Initial Values of Variables | publisher=Sun Microsystems | accessdateaccess-date=2008-10-17}}</ref> This differs from instance variables, which are implicitly initialized with default values (which are {{samp|0}} for numbers and {{samp|null}} for objects).

===Perl===

(Called ''lexical'', ''my'' or ''private'' variables.)

In Perl, local variables are declared using the <code>my</code> operator. Uninitialized scalars will have the value <code>undef</code>; uninitialized arrays or hashes will be <code>()</code>.<ref>{{cite web | url=http://perldoc.perl.org/perlsub.html#Private-Variables-via-my() | title=Private variables via my() - perlsub - perldoc.perl.org | publisher= | accessdateaccess-date=2008-10-17}}</ref>

Perl also has a <code>[[Local variable|local]]</code> operator that does not create automatic variables,<ref>{{cite web | url=http://perldoc.perl.org/perlsub.html#Temporary-Values-via-local%28%29 | title=Temporary values via local() - perlsub - perldoc.perl.org | publisher= | accessdateaccess-date=2011-02-25}}</ref> instead giving global (package) variables a temporary value, which is [[Scope_(computer_science)#Dynamic_scoping|dynamically scoped]] to the enclosing block. When the scope of the variable is left, the old value is restored.

==See also==