A array_map alternative for iterables

iterator_map.php

<?php

declare(strict_types = 1);

/**
 * Like array_map() but over an iterable, and it returns a new iterable with
 * mapping instead of a mapped array. The callable should take two arguments:
 * a value to map and its key in the stream.
 */
function iterator_map(callable $cb, iterable $itr): iterable {
   foreach ($itr as $key => $value) {
      yield $cb($value, $key);
   }
}