public function testGroupInverseRule()
{
$a = ListLike::unit(1, 2, 3);
$b = clone $a;
$b->inverse();
$result = ListLike::add($a, $b);
$this->assertEquals(ListLike::unit(), $result);
}
public static function add($a, $b)
{
if ($a->isInverse($b)) {
return ListLike::unit();
}
$flatten = array();
foreach ($a as $elem) {
array_push($flatten, $elem);
}
$a->rewind();
foreach ($b as $elem) {
array_push($flatten, $elem);
}
$b->rewind();
return (new \ReflectionClass("Monadic\\Type\\ListLike"))->newInstanceArgs($flatten);
}