Add Unpair operation.

docs/pages/api.rst

@@ -1090,6 +1090,34 @@ Signature: ``Collection::transpose();``
     $result = Collection::with($records)
         ->transpose();
 
+unpair
+~~~~~~
+
+Unpair a collection of pairs.
+
+Interface: `Unpairable`_
+
+Signature: ``Collection::unpair();``
+
+.. code-block:: php
+
+    $input = [
+        'k1' => 'v1',
+        'k2' => 'v2',
+        'k3' => 'v3',
+        'k4' => 'v4',
+    ];
+
+    $c = Collection::fromIterable($input)
+        ->unpair();
+
+    // [
+    //     ['k1', 'v1'],
+    //     ['k2', 'v2'],
+    //     ['k3', 'v3'],
+    //     ['k4', 'v4'],
+    // ];
+
 until
 ~~~~~
 
@@ -1346,6 +1374,7 @@ Interface: `Truthyable`_
 .. _Transformable: https://github.com/loophp/collection/blob/master/src/Contract/Transformation/Transformable.php
 .. _Transposeable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Transposeable.php
 .. _Truthyable: https://github.com/loophp/collection/blob/master/src/Contract/Transformation/Truthyable.php
+.. _Unpair: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unpairable.php
 .. _Untilable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Untilable.php
 .. _Unwrapable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unwrapable.php
 .. _Walkable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Walkable.php

spec/loophp/collection/CollectionSpec.php

@@ -1715,6 +1715,25 @@ public function it_can_truthy(): void
             ->shouldReturn(false);
     }
 
+    public function it_can_unpair(): void
+    {
+        $input = [
+            'k1' => 'v1',
+            'k2' => 'v2',
+            'k3' => 'v3',
+            'k4' => 'v4',
+        ];
+
+        $this::fromIterable($input)
+            ->unpair()
+            ->shouldIterateAs([
+                ['k1', 'v1'],
+                ['k2', 'v2'],
+                ['k3', 'v3'],
+                ['k4', 'v4'],
+            ]);
+    }
+
     public function it_can_until(): void
     {
         $collatz = static function (int $initial = 1): int {

src/Collection.php

@@ -65,6 +65,7 @@
 use loophp\collection\Operation\Tail;
 use loophp\collection\Operation\Times;
 use loophp\collection\Operation\Transpose;
+use loophp\collection\Operation\Unpair;
 use loophp\collection\Operation\Until;
 use loophp\collection\Operation\Unwrap;
 use loophp\collection\Operation\Walk;
@@ -580,6 +581,11 @@ public function truthy(): bool
         return $this->transform(new Truthy());
     }
 
+    public function unpair(): CollectionInterface
+    {
+        return $this->run(new Unpair());
+    }
+
     public function until(callable ...$callbacks): CollectionInterface
     {
         return $this->run(new Until(...$callbacks));

src/Contract/Collection.php

@@ -59,6 +59,7 @@
 use loophp\collection\Contract\Operation\Tailable;
 use loophp\collection\Contract\Operation\Timesable;
 use loophp\collection\Contract\Operation\Transposeable;
+use loophp\collection\Contract\Operation\Unpairable;
 use loophp\collection\Contract\Operation\Untilable;
 use loophp\collection\Contract\Operation\Unwrapable;
 use loophp\collection\Contract\Operation\Walkable;
@@ -226,6 +227,7 @@ interface Collection extends
     Transformable,
     Transposeable,
     Truthyable,
+    Unpairable,
     Untilable,
     Unwrapable,
     Walkable,

src/Contract/Operation/Unpairable.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Contract\Operation;
+
+use loophp\collection\Contract\Collection;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ */
+interface Unpairable
+{
+    /**
+     * @return \loophp\collection\Contract\Collection<int, array{TKey, T}>
+     */
+    public function unpair(): Collection;
+}

src/Operation/Unpair.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use Iterator;
+use loophp\collection\Contract\Operation;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ */
+final class Unpair extends AbstractOperation implements Operation
+{
+    public function __invoke(): Closure
+    {
+        return
+            /**
+             * @psalm-param \Iterator<TKey, T> $iterator
+             *
+             * @psalm-return \Generator<TKey, T>
+             */
+            static function (Iterator $iterator): Generator {
+                foreach ($iterator as $key => $value) {
+                    yield [$key, $value];
+                }
+            };
+    }
+}