zipWithNext() operation

src/Operations/Stateless/ZippingWithNextSequence.php

@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BradynPoulsen\Sequences\Operations\Stateless;
+
+use BradynPoulsen\Sequences\DeferredIterator;
+use BradynPoulsen\Sequences\Iteration\Iterations;
+use BradynPoulsen\Sequences\Sequence;
+use BradynPoulsen\Sequences\Traits\CommonOperationsTrait;
+use Generator;
+use Traversable;
+
+/**
+ * @internal
+ */
+final class ZippingWithNextSequence implements Sequence
+{
+    use CommonOperationsTrait;
+
+    /**
+     * @var Sequence
+     */
+    private $previous;
+
+    /**
+     * @var callable (T $a, T $b) -> R
+     */
+    private $transform;
+
+    public function __construct(Sequence $previous, ?callable $transform = null)
+    {
+        $this->previous = $previous;
+        $this->transform = $transform ?? function ($a, $b): array {
+            return [$a, $b];
+        };
+    }
+
+    public function getIterator(): Traversable
+    {
+        return new DeferredIterator(function (): Generator {
+            $iteration = Iterations::fromTraversable($this->previous->getIterator());
+            if (!$iteration->hasNext()) {
+                return;
+            }
+            $current = $iteration->pluckNext();
+            while ($iteration->hasNext()) {
+                $next = $iteration->pluckNext();
+                yield call_user_func($this->transform, $current, $next);
+                $current = $next;
+            }
+        });
+    }
+}

src/Sequence.php

@@ -754,4 +754,16 @@ public function windowed(
      * @return Sequence Sequence<A> -> Sequence<R>
      */
     public function zip(Sequence $other, ?callable $transform = null): Sequence;
+
+    /**
+     * Returns a sequence containing the results of applying the given $transform function, if provided, to an each pair
+     * of two adjacent elements in this sequence.
+     *
+     * @effect intermediate
+     * @state stateless
+     *
+     * @param callable|null $transform (T $a, T $b) -> R
+     * @return Sequence Sequence<T> -> Sequence<R>
+     */
+    public function zipWithNext(?callable $transform = null): Sequence;
 }

src/Traits/StatelessOperationsTrait.php

@@ -14,7 +14,8 @@
     TakeSequence,
     TakeWhileSequence,
     TransformingSequence,
-    ZippingSequence
+    ZippingSequence,
+    ZippingWithNextSequence
 };
 use BradynPoulsen\Sequences\Sequence;
 use InvalidArgumentException;
@@ -161,4 +162,12 @@ public function zip(Sequence $other, ?callable $transform = null): Sequence
     {
         return new ZippingSequence($this, $other, $transform);
     }
+
+    /**
+     * @see Sequence::zipWithNext()
+     */
+    public function zipWithNext(?callable $transform = null): Sequence
+    {
+        return new ZippingWithNextSequence($this, $transform);
+    }
 }