Closure (computer programming): Difference between revisions

Revision as of 19:18, 13 May 2024

Revision as of 18:11, 19 July 2024

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The nested function definitions are not themselves closures: they have a free variable which is not yet bound. Only once the enclosing function is evaluated with a value for the parameter is the free variable of the nested function bound, creating a closure, which is then returned from the enclosing function.

Lastly, a closure is only distinct from a function with free variables when outside of the scope of the non-local variables, otherwise the defining environment and the execution environment coincide and there is nothing to distinguish these (static and dynamic binding cannot be distinguished because the names resolve to the same values). For example, in the below program below, functions with a free variable <code>x</code> (bound to the non-local variable <code>x</code> with global scope) are executed in the same environment where <code>x</code> is defined, so it is immaterial whether these are actually closures:

<syntaxhighlight lang="python">

x = 1