Merge pull request #74 from MortalFlesh/feature/add-partition

Add IList::partition method

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 <!-- There is always Unreleased section on the top. Subsections (Add, Changed, Fix, Removed) should be Add as needed. -->
 ## Unreleased
+- Add `Immutable/Generic/IList::partition` method
 
 ## 7.1.1- 2023-11-25
 - Fix return type of `sortBy` and `sortByDescending` methods

src/Immutable/Generic/IList.php

@@ -247,6 +247,15 @@ public function max(): mixed;
      */
     public function maxBy(callable $callback): mixed;
 
+    /**
+     * Splits the collection into two collections, containing the elements for which the given predicate returns True and False respectively.
+     * Element order is preserved in both of the created lists.
+     *
+     * @phpstan-param callable(TValue, TIndex=): bool $predicate
+     * @phpstan-return array{0:IList<TValue>, 1: IList<TValue>}
+     */
+    public function partition(callable $predicate): array;
+
     /** @phpstan-return \MF\Collection\Mutable\Generic\IList<TValue> */
     public function asMutable(): \MF\Collection\Mutable\Generic\IList;
 

src/Immutable/Generic/ListCollection.php

@@ -710,6 +710,30 @@ public function maxBy(callable $callback): mixed
         return $max;
     }
 
+    /**
+     * Splits the collection into two collections, containing the elements for which the given predicate returns True and False respectively.
+     * Element order is preserved in both of the created lists.
+     *
+     * @phpstan-param callable(TValue, TIndex=): bool $predicate
+     * @phpstan-return array{0:IList<TValue>, 1: IList<TValue>}
+     */
+    public function partition(callable $predicate): array
+    {
+        $predicate = Callback::curry($predicate);
+
+        $trueList = [];
+        $falseList = [];
+        foreach ($this as $i => $v) {
+            if ($predicate($v, $i)) {
+                $trueList[] = $v;
+            } else {
+                $falseList[] = $v;
+            }
+        }
+
+        return [new static($trueList), new static($falseList)];
+    }
+
     /** @phpstan-return \MF\Collection\Mutable\Generic\IList<TValue> */
     public function asMutable(): \MF\Collection\Mutable\Generic\IList
     {

tests/Fixtures/SimpleEntity.php

@@ -4,6 +4,11 @@
 
 class SimpleEntity implements EntityInterface
 {
+    public static function create(int $id): self
+    {
+        return new self($id);
+    }
+
     public function __construct(private int $id)
     {
     }

tests/Immutable/Generic/ListTest.php

@@ -847,4 +847,48 @@ public function testShouldMapListAndUseIndexInMapping(): void
 
         $this->assertSame([0, 2, 6, 12, 20], $list->toArray());
     }
+
+    /** @dataProvider provideListForPartition */
+    public function testShouldPartitionList(IList $list, callable $predicate, array $expected): void
+    {
+        $actual = $list->partition($predicate);
+
+        $this->assertEquals($expected, $actual);
+    }
+
+    public static function provideListForPartition(): array
+    {
+        return [
+            // list, predicate, expected
+            'empty' => [
+                new ListCollection(),
+                fn (int $i) => $i % 2 === 0,
+                [new ListCollection(), new ListCollection()],
+            ],
+            'even/odd' => [
+                Seq::range('0..10')->toList(),
+                fn (int $i) => $i % 2 === 0,
+                [
+                    ListCollection::from([0, 2, 4, 6, 8, 10]),
+                    ListCollection::from([1, 3, 5, 7, 9]),
+                ],
+            ],
+            'even/odd (no odds)' => [
+                Seq::range('0..10')->toList()->filter(fn (int $i) => $i % 2 === 0),
+                fn (int $i) => $i % 2 === 0,
+                [
+                    ListCollection::from([0, 2, 4, 6, 8, 10]),
+                    ListCollection::from([]),
+                ],
+            ],
+            'objects' => [
+                Seq::range('0..10')->toList()->map(SimpleEntity::create(...)),
+                fn (SimpleEntity $entity) => $entity->getId() > 5,
+                [
+                    Seq::range('6..10')->toList()->map(SimpleEntity::create(...)),
+                    Seq::range('0..5')->toList()->map(SimpleEntity::create(...)),
+                ],
+            ],
+        ];
+    }
 }