identity() public static méthode

Get an identity function.
public static identity ( ) : callable
Résultat callable A function that returns its first argument.
Functions Class Documentation
Exemple #1
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 /**
  * Test the Functions::identity method.
  */
 public function testIdentity()
 {
     $data = ['foo', 'bar', 42];
     $identityFunc = Functions::identity();
     $this->assertTrue(is_callable($identityFunc), "Identity function should be callable.");
     foreach ($data as $item) {
         $this->assertEquals($item, $identityFunc($item));
     }
 }
Exemple #2
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 /**
  * Flatten the underlying stream.
  *
  * This method takes each element and unpacks it into a sequence of elements.
  * All individual sequences are concatenated in the resulting stream.
  *
  * @param callable $unpacker [optional] An unpacker function that can unpack
  * elements into something iterable. Default is to use the identity function.
  * @return Stream
  */
 public function flatMap(callable $unpacker = null)
 {
     if ($unpacker == null) {
         $unpacker = Functions::identity();
     }
     return new FlatMapOperation($this, $unpacker);
 }