category-2.1-3

gistfile1.js

//only works for single argument functions
function compose(g, f) { return function (x) { return g(f(x))} ; }

function id(x) { return x; }

function add_one(x) { return x + 1; }
function times_two(x) { return x * 2; }

var two_x_plus_1 = compose(add_one, times_two);

console.log(two_x_plus_1(1)); //3
console.log(two_x_plus_1(3)); //7
console.log(two_x_plus_1(-4)); //-7

console.log(compose(two_x_plus_1, id)(1)); //3
console.log(compose(two_x_plus_1, id)(3)); //7
console.log(compose(two_x_plus_1, id)(-4));//-7