Online PHP editor | refs for SeSbN

<?php function chain($iterable, array $functions) { foreach ($functions as $function) { $iterable = $function(as_iterator($iterable)); } } function as_iterator($iterable) { if ($iterable instanceof \Iterator) { return $iterable; } if (is_array($iterable)) { return new \ArrayIterator($iterable); } if (is_string($iterable)) { return new \ArrayIterator(str_split($iterable)); } throw new \Exception(); } function do_map(callable $function) { return function(Iterator $iterator) use ($function) { foreach ($iterator as $key => $value) { yield $key => $value; } }; } function do_filter(callable $function) { return function(Iterator $iterator) use($function) { foreach ($iterator as $key => $value) { if ($function($value, $key)) { yield $key => $value; } } }; } function do_concat($iterable) { return function(Iterator $iterator) use ($iterable) { foreach ($iterator as $value) { yield $value; } foreach (as_iterator($iterable) as $value) { yield $value; } }; } function do_as_array() { return function(Iterator $iterator) { return iterator_to_array($iterator); }; } $array = chain([1, 2, 3, 4], [ do_concat([5, 6, 7, 8]), do_filter(function ($v) { return $v % 2 == 0; }), do_map(function ($v) { return $v * 3; }), do_as_array(), ]);