Implement removeAll for Set (#85)

* Implement removeAll for Set

* Add more tests

Author: akondas

src/Collection/Set.php

@@ -109,6 +109,23 @@ public function remove($element): self
         return self::fromPointer($elements);
     }
 
+    /**
+     * @param Set<T> $elements
+     *
+     * @return Set<T>
+     */
+    public function removeAll(Set $elements): self
+    {
+        $new = [];
+        foreach ($this->elements as $current) {
+            if (!$elements->contains($current)) {
+                $new[] = $current;
+            }
+        }
+
+        return self::fromPointer($new);
+    }
+
     /**
      * @param Set<T> $set
      *

tests/Collection/SetTest.php

@@ -248,4 +248,20 @@ public function testFlatMap(): void
             Set::ofAll([1, 2, 4, 3, 6])
         ));
     }
+
+    public function testSetRemoveAll(): void
+    {
+        $set = Set::ofAll(['alpha', 'beta', 'gamma']);
+        $new = $set->removeAll(Set::ofAll(['beta', 'gamma']));
+
+        self::assertFalse($new->contains('beata'));
+        self::assertFalse($new->contains('gamma'));
+        self::assertTrue($set !== $new);
+        self::assertEquals(1, $new->length());
+
+        self::assertTrue(Set::ofAll(['alpha', 'beta', 'gamma'])->removeAll(Set::empty())->equals(Set::ofAll(['alpha', 'beta', 'gamma'])));
+        self::assertTrue(Set::ofAll(['alpha', 'beta', 'gamma'])->removeAll(Set::ofAll(['alpha', 'beta', 'gamma']))->equals(Set::empty()));
+        self::assertTrue(Set::ofAll(['alpha', 'beta', 'gamma'])->removeAll(Set::ofAll(['1', '2', '3']))->equals(Set::ofAll(['alpha', 'beta', 'gamma'])));
+        self::assertTrue(Set::ofAll(['alpha', 'beta', 'gamma'])->removeAll(Set::ofAll(['1', '2', 'gamma']))->equals(Set::ofAll(['alpha', 'beta'])));
+    }
 }