/**
* emptyM :: a
*
* @param Monoid $a
*
* @return Monoid
*/
function emptyM(Monoid $a)
{
return $a->getEmpty();
}
public function bind(callable $function)
{
list($value, $side) = call_user_func($function, $this->value)->runWriter();
return new static($value, $this->side->concat($side));
}
