/**
* Over
*
* Perform an operation over the focus of a lens. Returns the entire object
* as passed in, but with the given function run over a portion of it. Is similar to composing
* a set and a get operation all at once.
*
* @example
* $myLens = Lens::indexLens('a');
* Lens::overL($myLens, Math::add(1), ['a' => 1]; // ['a' => 2]
*
* @note Depending on which lens you use, this method might throw an exception.
* Refer to the indivual lenses to see if they're safe to use or not.
*
* @param callable|Lens $lens Lens to use when viewing an object
* @param Mixed $x Object or array to view
* @return mixed The property that the lens focused on
* @internal param Lens $ a -> a
*/
protected static function __overL(callable $lens, $f, $x)
{
$over = Lambda::compose(Functor::extract(), $lens(Lambda::compose(Identity::identity(), $f)));
return $over($x);
}
/**
* Identity a => apply (Identity f) (a) === fmap f a
* @param Identity $a
* @return mixed
*/
public function apply($a)
{
return $a->fmap($this->heldValue);
}
