From 02c61a141a553af9767656acd7fa863ac2710ec5 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Wed, 18 Aug 2021 22:05:51 +0200
Subject: [PATCH] refactor: Update `Collapse` operation in point free style.
 (#182)

---
 src/Operation/Collapse.php | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/src/Operation/Collapse.php b/src/Operation/Collapse.php
index b77855262..f57b6f0ad 100644
--- a/src/Operation/Collapse.php
+++ b/src/Operation/Collapse.php
@@ -28,24 +28,19 @@ final class Collapse extends AbstractOperation
      */
     public function __invoke(): Closure
     {
-        return
+        $filterCallback =
             /**
-             * @param Iterator<TKey, iterable<TKey, T>|T> $iterator
-             *
-             * @return Generator<TKey, T>
+             * @param T $value
              */
-            static function (Iterator $iterator): Generator {
-                /** @var Closure(Iterator<TKey, T|iterable<TKey, T>>): Generator<TKey, iterable<TKey, T>> $filter */
-                $filter = Filter::of()(
-                    /**
-                     * @param T $value
-                     */
-                    static fn ($value): bool => is_iterable($value)
-                );
+            static fn ($value): bool => is_iterable($value);
 
-                foreach ($filter($iterator) as $value) {
-                    yield from $value;
-                }
-            };
+        /** @var Closure(Iterator<TKey, (T|iterable<TKey, T>)>): Generator<TKey, T> $pipe */
+        $pipe = Pipe::of()(
+            Filter::of()($filterCallback),
+            Flatten::of()(1),
+        );
+
+        // Point free style.
+        return $pipe;
     }
 }