/**
* Generic test to verify if a type obey the functor laws.
*
* @param callable $assertEqual Asserting function (Functor $f1, Functor $f2, $message)
* @param callable $f (a -> b)
* @param callable $g (a -> b)
* @param Functor $x f a
*/
public static function test(callable $assertEqual, callable $f, callable $g, Functor $x)
{
// identity: fmap id == id
$assertEqual(f\map(f\identity, $x), $x, 'identity');
// composition: fmap (f . g) == fmap f . fmap g
$assertEqual(f\map(f\compose($f, $g), $x), call_user_func(f\compose(f\map($f), f\map($g)), $x), 'composition');
}
public function test_it_should_retun_function_accepting_arguments()
{
$this->assertInstanceOf(\Closure::class, f\compose('strtolower', 'strtoupper'));
}
/**
* Adapt function that may throws exceptions to Either monad.
*
* tryCatch :: Exception e => (a -> b) -> (e -> c) -> a -> Either c b
*
* @param callable $function (a -> b)
* @param callable $catchFunction (e -> c)
* @param mixed $value a
*
* @return Either|\Closure
*/
function tryCatch(callable $function = null, callable $catchFunction = null, $value = null)
{
return call_user_func_array(f\curryN(3, function (callable $function, callable $catchFunction, $value) {
return f\tryCatch(f\compose(right, $function), f\compose(left, $catchFunction), $value);
}), func_get_args());
}