phpstreams\Stream::reduce PHP Method

Stream Class Documentation Usage Examples Of phpstreams\Stream::reduce Show file Open project: bertptrs/phpstreams

reduce() public method

The given is applied to every item in the stream in no particular order. The result is then returned. In order for the callable to be a proper reductor, it should be:
  • Commutative, so op($a, $b) is equal to op($b, $a), and
  • Should preserve respect the given identity, i.e. op($a, $identity) = $identity.
If any of these properties do not hold, the output of this function is not defined.
public reduce ( mixed $identity, callable $binaryOp ) : mixed
$identity mixed The identity element.
$binaryOp callable A reduction function, respecting the properties above.
return mixed 
    public function reduce($identity, callable $binaryOp)
    {
        $cur = $identity;
        foreach ($this as $value) {
            $cur = $binaryOp($cur, $value);
        }
        return $cur;
    }

Usage Example

Example #1
0
 public function testReduce()
 {
     $instance = new Stream([1, 2, 3, 4]);
     $result = $instance->reduce(0, function ($a, $b) {
         return $a + $b;
     });
     $this->assertEquals(10, $result);
 }
Stream
__construct
all
any
collect
count
distinct
filter
flatMap
getIterator
isSorted
isValidSource
limit
map
reduce
skip
sorted
toArray