dikini.net

Closure

Intent: Create first class behaviours capable of storing state between use
Motivation: We want to maintain the history of computation, an maybe save and reuse the computation at a particular point in time
Implementation: The basic implementation is invisible in php - static variables in functions (but that doesn't allow us to have the usual features of a language with closures because functions in php are not first class objects, i.e we can't copy them), objects (they get us there, albeit more verbously). The examples below are borrowed from io-reader: php closures. Read the post and the full code to understand the full implementation.
Example: // fixed-point combinator function Y(Lambda &$le) { return lambda(get_defined_vars(), 'Lambda $f', ' return $f->call($f); ')->call(lambda(get_defined_vars(), 'Lambda $f', ' return $le->call(lambda(get_defined_vars(), \'$x\', \' return $f->call($f)->call($x); \')); ')); }
Note: Closures and objects are dual, compare behaviour with state and state with behaviours
Yet another note:: Alternatively have a look at this implementation or my emulating closures in php blurb
Final note:: All this is better avoided in php - too many underwater rocks

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