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@ 2016-01-13T22:46:28Z

<?php


function combinations(int $n, int $k):array
{
    function combine(int $n, int $k, int $start = 0, array &$result = [], array &$all = [])
    {
        if ($k == 0) {
            $all[] = $result;
            return;
        }

        for ($i = $start; $i <= $n - $k; $i++) {
            $result[$k] = $i;
            combine($n, $k - 1,  $i + 1, $result, $all);
        }
    }

    $res = [];
    $all = [];

    combine($n, $k, 0, $res, $all);

    return $all;
}

function may_add_combination_to_set(array $combination, array $sets)
{
    foreach ($sets as $combinationInSet) {
        if (count(array_intersect($combinationInSet, $combination)) !== 1) {
            return false;
        }
    }

    return true;
}


$combinations = combinations(31, 6);

$sets = [];

foreach ($combinations as $combination) {
    if (may_add_combination_to_set($combination, $sets)) {
        $sets[] = $combination;
    }
}

count($sets);

Output for git.master, rfc.property-hooks: Fatal error: Out of memory (allocated 35655680 bytes) (tried to allocate 20480 bytes) in /in/vq7d6 on line 14 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.
Output for git.master_jit: Fatal error: Out of memory (allocated 18874368 bytes) (tried to allocate 20480 bytes) in /in/vq7d6 on line 14 mmap() failed: [12] Cannot allocate memory mmap() failed: [12] Cannot allocate memory
Process exited with code 255.

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2020-03-21 RFC: Is_Literal - declined
2020-12-04 Enumerations - included in PHP 8.1
2018-06-15 Typed Properties v2 - implemented in PHP 7.4
2016-08-12 Object typehint - included in PHP 7.2
2016-08-14 Arrow functions - withdrawn
2016-05-29 array_change_keys() - withdrawn
2016-04-19 Lexical scope support for anonymous classes - suspended
2016-04-17 Functional Interfaces - declined
2016-03-16 Typed Properties - superseded in favor of Typed Properties 2.0
2015-08-27 Callable Prototypes - declined
2015-05-01 Short Closures - declined / withdrawn in favor of Arrow Functions
2015-02-18 Scalar type hints v5 - included in PHP 7
2015-02-14 Union Types - declined
2013-09-22 Anonymous classes - included in PHP 7

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