javascript-the-good-parts

function identity(x){
	return x;
}

function add(a, b){
	return a+b;
}

function mul(a, b){
	return a*b;
}

function identityf(x){
	return function(){
		return x;
	}
}

function addf(x){
	return function(y){
		return x+y;
	}
}

function applyf(func){
	return function(x){
      return function(y){
		return func(x, y);
	  }
	}
}

function curry(func, a){
	return function(b){
		return func(a, b);
	}
}

curry(function(a, b){ return a*b;}, 5)(6);

//1
inc = addf(1);
inc(5);
//2
inc = applyf(add)(1);
inc(5);
//3
inc = curry(add, 1)
inc(5);

function methodize(func){
	return function(n){
		return func.call(null, this, n);
	}
};
Number.prototype.add = methodize(add);
(3).add(4);

function demethodize(func){
	return function(that, b){
		return func.call(that, b);
	}
}
demethodize(Number.prototype.add)(5, 6);

function twice(func){
	return function(x){
		return func.call(null, x, x);
	}
}
var double = twice(add);
double(11);

var square = twice(mul);
square(11);

function composeu(func1, func2){
	return function(x){
		return func2(func1(x));
	}
}
composeu(double, square)(3);

function composeb(func1, func2){
	return function(a, b, c){
		return func2(func1(a, b), c);
	}
}
composeb(add, mul)(2, 3, 5);


function once(func){
	return function(){
		var f = func;
		func = null;
		return f.apply(this, arguments);
	}
}
var add_once = once(add);
add_once(3, 4);
//add_once(3, 4);


function counterf(n){
	return {
		inc: function(){
			n += 1;
			return n;
		},
		dec: function(){
			n -= 1;
			return n;
		}
	}
}
var counter = counterf(10);
counter.inc();
counter.dec();

function alert(n){
	return n;
}
function revocable(nice){
	return {
		invoke: function(){
			return nice.apply(this, arguments);
		},
		revoke: function(){
			func = null;
		}
	}
}
var tmp = revocable(alert);
tmp.invoke(7);
tmp.revoke(7);
//tmp.invoke(8);

//1
function MONAD(){
	return function unit(value){
		var monad = Object.create(null);
		monad.bind = function(){
			return func(value);
		}
		return monad;
	}
}


//2
function MONAD(){
	var prototype = Object.create(null);
	return function unit(value){
		var monad = Object.create(prototype);
		monad.bind = function(func, args){
			return func.apply( undefined, [value].concat(Array.prototype.slice.apply(args || [])) );
		}
		return monad;
	}
	//1
	unit.method = function(name, func){
		prototype[name] = func;
		return unit;
	}
	//2
	unit.lift = function(name, func){
		prototype[name] = function(args){
			return unit( 
				this.bind( func, [value].concat(Array.prototype.slice.apply(args || [])) ) 
				);
		}
	}
	return unit;
}