Merge pull request #20 from jejung/feature/distinct

introduce distinct  function

Author: killertux

src/Stream.php

@@ -91,6 +91,36 @@ public static function rangeFloat(float $start, float $end, float $step = 1): se
 		return self::range($start, $end, $step);
 	}
 
+	/**
+	 * Returns a new stream containing only unique values from this stream.
+	 *
+	 * By default, objects are compared to their ids (through <code>spl_object_id()</code>), pass
+	 * in a <code>callable $id</code> to change this behavior.
+	 *
+	 * Items are yielded by the order of their first occurrence.
+	 *
+	 * @param callable|null $id can be used to change items identity, by default <code>is_object($item) ? spl_object_id($item) : $item</code> is used.
+	 * @return self
+	 */
+	public function distinct(callable $id = null): self {
+		if (is_null($id)) {
+			$id = fn ($item) => is_object($item) ? spl_object_id($item) : $item;
+		}
+		$generator = function () use ($id) {
+			$visited = [];
+			foreach ($this->source_iterator as $item) {
+				$item_id = $id($item);
+				if (array_key_exists($item_id, $visited)) {
+					continue;
+				}
+				$visited[$item_id] = true;
+				yield $item;
+			}
+		};
+
+		return new self($generator());
+	}
+
 	/**
 	 * Collects all stream elements into an array.
 	 *

test/StreamTest.php

@@ -7,6 +7,20 @@
 
 class StreamTest extends TestCase {
 
+	public function testDistinct() {
+		$cls = new class () {};
+
+		$a = new $cls();
+		$b = new $cls();
+
+		$this->assertEquals([], Stream::of([])->distinct()->collect());
+		$this->assertEquals([1], Stream::of([1])->distinct()->collect());
+		$this->assertEquals([1], Stream::of([1, 1])->distinct()->collect());
+		$this->assertEquals([true, false], Stream::of([true, false])->distinct()->collect());
+		$this->assertEquals([$a, $b], Stream::of([$a, $b, $a])->distinct()->collect());
+		$this->assertEquals([true, false], Stream::of([true, false, false, null, 0])->distinct($id=fn ($item) => !$item)->collect());
+	}
+
 	public function testStreamIsCountable(): void {
 		$this->assertCount(0, Stream::of([]));
 		$this->assertCount(1, Stream::of(['a']));