<?php

namespace PhatCats\ObjectTypeclass;

trait ObjectMonad {

use ObjectApplicative;

/**

* @param callable $f A function of one argument whose type is the type of

* value contained in the monad. The return type of $f should be the same as

* this monad, i.e., if this monad is a Maybe, then the return type of $f

* should be a Maybe.

* @return The value returned by $f.

*/

abstract function flatMap(callable $f);

/**

* Removes one layer of structure.

* @return The type of the return value should be the same type as this ObjectMonad.

*/

function join() {

// the identity function. Can you believe PHP doesn't have one in the

// standard lib?

$id = function ($x) { return $x; };

return $this->flatMap($id);

}

}