/**
* This method returns a "cons" object for a choice.
*
* @access public
* @static
* @param Core\Equality\Type $x the object to be evaluated
* @param Control\Choice\Type $xs the tail
* @return Control\Choice\Type the "cons" object
*/
public static function cons(Core\Equality\Type $x, Control\Choice\Type $xs) : Control\Choice\Type
{
if ($xs !== null) {
return new Control\Choice\Cons\Type($x, $xs);
}
return new Control\Choice\Cons\Type($x, Control\Choice\Type::nil());
}
/**
* This method sets the procedure that will be executed should "y" equal "x".
*
* @access public
* @final
* @param Core\Equality\Type $y the object to be evaluated
* against
* @param callable $procedure the procedure to be executed
* @return Control\Choice\Type a reference to the next choice
* monad node
*/
public final function when(Core\Equality\Type $y, callable $procedure) : Control\Choice\Type
{
$this->predicate = function ($x) use($y, $procedure) {
if ($y->__eq($x)) {
IUnit\Type::covariant($procedure($x));
return true;
}
return false;
};
return Control\Choice\Type::cons($this->x, $this);
}
/**
* This method returns a choice monad for evaluating an object.
*
* @access public
* @static
* @param Core\Equality\Type $x the object to be evaluated
* @return Control\Choice\Type the choice monad
*/
public static function choice(Core\Equality\Type $x) : Control\Choice\Type
{
return Control\Choice\Type::cons($x, Control\Choice\Type::nil());
}
