Non-local variable: Difference between revisions

Revision as of 13:43, 24 September 2017

Revision as of 10:07, 25 July 2020

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=== Nested functions === <!-- Please do NOT add the same example in other languages to this article. These two examples suffice to get the point across. Wikipedia is not a source code repository. -->

In the Python 3 example that follows there is a nested function <code>inner</code> defined in the scope of another function <code>outer</code>. The variable <code>x</code> is local to <code>outer</code>, but non-local to <code>inner</code> (nor is it global):

<sourcesyntaxhighlight lang=python3>

def outer():

x = 1

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print(x)

return inner

</syntaxhighlight>

</source>

In Javascript, the locality of a variable is determined by the closest <code>var</code> statement for this variable. In the following example, <code>x</code> is local to <code>outer</code> as it contains a <code> var x</code> statement, while <code>inner</code> doesn't. Therefore, x is non-local to <code>inner</code>:

<sourcesyntaxhighlight lang=javascript>

function outer() {

var x = 1;

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return inner;

}

</syntaxhighlight>

</source>

=== Anonymous functions === <!-- Please do NOT add the same example in other languages to this article. These examples suffice to get the point across. Wikipedia is not a source code repository. -->

In the Haskell example that follows the variable <code>c</code> is non-local in the anonymous function <code>\x -> x + c</code>:

<sourcesyntaxhighlight lang=haskell>

outer = let c = 1 in map (\x -> x + c) [1, 2, 3, 4, 5]

</syntaxhighlight>

</source>

== Implementation issues ==