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<?php

namespace Functional;

/**

* Decorates given function with tail recursion optimization.

*

* I took solution here https://gist.github.com/beberlei/4145442

* but reworked it and make without classes.

*

* @param callable $fn

* @return callable

*/

function tail_recursion(callable $fn): callable

{

$underCall = false;

$queue = [];

return function (...$args) use (&$fn, &$underCall, &$queue) {

$result = null;

$queue[] = $args;

if (!$underCall) {

$underCall = true;

while ($head = \array_shift($queue)) {

$result = $fn(...$head);

}

$underCall = false;

}

return $result;

};

}