Add Stream::init method

Author: klimick

src/Fp/Functions/Collection/Init.php

@@ -6,6 +6,8 @@
 
 use Fp\Operations\InitOperation;
 
+use function Fp\Cast\asArray;
+
 /**
  * @template TK of array-key
  * @template TV
@@ -16,5 +18,5 @@
  */
 function init(iterable $collection): array
 {
-    return InitOperation::of($collection)();
+    return asArray(InitOperation::of($collection)());
 }

src/Fp/Operations/InitOperation.php

@@ -4,6 +4,8 @@
 
 namespace Fp\Operations;
 
+use Generator;
+
 /**
  * @template TK
  * @template TV
@@ -13,13 +15,25 @@
 final class InitOperation extends AbstractOperation
 {
     /**
-     * @return array<TK, TV>
+     * @return Generator<TK, TV>
      */
-    public function __invoke(): array
+    public function __invoke(): Generator
     {
-        $butLast = iterator_to_array($this->gen);
-        array_pop($butLast);
+        if (!$this->gen->valid()) {
+            return [];
+        }
+
+        while (true) {
+            $item = $this->gen->current();
+            $key = $this->gen->key();
+
+            $this->gen->next();
+
+            if (!$this->gen->valid()) {
+                break;
+            }
 
-        return $butLast;
+            yield $key => $item;
+        }
     }
 }

src/Fp/Streams/Stream.php

@@ -388,6 +388,16 @@ public function tail(): Stream
         return $this->fork(Ops\TailOperation::of($this->emitter)());
     }
 
+    /**
+     * {@inheritDoc}
+     *
+     * @return Stream<TV>
+     */
+    public function init(): Stream
+    {
+        return $this->fork(Ops\InitOperation::of($this->emitter)());
+    }
+
     /**
      * {@inheritDoc}
      *

src/Fp/Streams/StreamChainableOps.php

@@ -203,6 +203,18 @@ public function mapN(callable $callback): Stream;
      */
     public function tail(): Stream;
 
+    /**
+     * Returns every stream element except last
+     *
+     * ```php
+     * >>> Stream::emits([1, 2, 3])->init()->toList();
+     * => [1, 2]
+     * ```
+     *
+     * @return Stream<TV>
+     */
+    public function init(): Stream;
+
     /**
      * Take stream elements while predicate is true
      *

tests/Runtime/Classes/Stream/StreamOpsTest.php

@@ -217,6 +217,14 @@ public function testTail(): void
         );
     }
 
+    public function testInit(): void
+    {
+        $this->assertEquals(
+            [1, 2],
+            Stream::emits([1, 2, 3])->init()->toList(),
+        );
+    }
+
     public function testTakeAndDrop(): void
     {
         $this->assertEquals([0, 1], Stream::emits([0, 1, 2])->takeWhile(fn($e) => $e < 2)->toList());