loophp / collection

src/Operation/Unzip.php

<?php

declare(strict_types=1);

namespace loophp\collection\Operation;

use Closure;
use Generator;

/**
 * @immutable
 *
 * @template TKey
 * @template T
 */
final class Unzip extends AbstractOperation
{
    /**
     * @return Closure(iterable<TKey, list<T>>): Generator<int, list<T>>
     */
    public function __invoke(): Closure
    {
        $reduceCallback =
            /**
             * @param array<int, list<T>> $carry

The doc comment array<int, list<T>> at position 4 could not be parsed: Expected '>' at position 4, but found 'list'.

             * @param iterable<TKey, T> $value
             *
             * @return array<int, list<T>>

The doc comment array<int, list<T>> at position 4 could not be parsed: Expected '>' at position 4, but found 'list'.

             */
            static function (array $carry, iterable $value): array {
                $index = 0;

The assignment to $index is dead and can be removed.

                foreach ($value as $carry[$index++][]);

                return $carry;
            };

        /** @var Closure(iterable<TKey, list<T>>): Generator<int, list<T>> $pipe */
        $pipe = (new Pipe())()(
            (new Reduce())()($reduceCallback)([]),
            (new Flatten())()(1)
        );

        // Point free style.
        return $pipe;
    }
}