gistfile1.hs

this is sample code

-- factorial. n! = 1 * 2 * 3 * ... * ( n - 1)
fact :: Int -> Int = F fact
-- Functor function for factorial
F f x :: (Int -> Int) -> Int -> Int = 1 if 0 `is` x else x * f $ x - 1

-- Instead, functions define without Type Binding. 
-- But, it maybe do unexpected work
fact2 = F2 fact2 -- fact2 :: Num a => a -> a
F2 f x = 1 if 0 `is` x else x * f $ x - 1 -- F2 :: Num a => (a -> a) -> a -> a



-- those code compile to javascript sush as ...

/**
 * @param  {number} x
 * @return  {number}
 */
function fact ( x ) {
	return ( 0 == x ) ? 1 : x * fact ( x - 1 );
}

/**
-- create nothing too much functor method.
-- compiler give code most smart solution
**/

/**
 * when, compile option --paformance
 * compiler think tail call optimization and halting problem
 * @param {!number} x
 * @return {!number}
 */
function fact2 ( x ) {
	if ( typeof x != "number" || Math.abs( x % 1 ) != 0 ) {
		throw new Error ( "Illegal Arguments Type. It's must be Integral" );
	}
	if ( x < 0 ) {
		throw new Error ( "Unexpected Infinite Loop : " + x );
	}
        /** @type {!number} **/
	var _r = 1;
	while ( x > 0 ) {
		_r = x-- * _r;
	}
	return _r;
};