/**
* Invoke a value if it is callable.
*
* @param array $args optional array of arguments to pass to the optional callable
* @return Chain the result of the invocation wrapped into a Chain, or empty Chain
*/
public function invokeArray(array $args = []) : Chain
{
return $this->continue(conditionally(is_callable, curry(reverse(call_user_func_array), 2)($args)));
}
/**
* Iteratively reduce the stream to a single value using a callback function.
*
* Method applies iteratively the callback function to elements and keys of
* the stream, so as to reduce it to a single value.
*
* This is a closing operation (it calls <code>$this->close()</code> internally).
*
* @param callable $callback the callback to apply to each element and key;
* current intermediate result will be passed as the first argument
* (in the case of the first iteration it instead holds the value of $initial),
* current value will be passed as the second one, current key will be passed
* as the third one; callback must return new intermediate result
* @param mixed $initial initial value (optional, default is NULL)
* @return Optional an optional result
* @see \convert\traversable_reduce
* @see \monad\Stream::close()
*/
public function reduce(callable $callback, $initial = null) : Optional
{
return $this->bindMonad(sequence(curry(traversable_reduce, 3)($callback)($initial), optional));
}
