function sequence(start, step) {
	var x = 0;
	return function () {
		start = start || 0;
		step = step || 1;
		var y = start + (step * x)
		x++;
		return y;
	}
}
 
 
var gen = sequence(1, 1);
 
 
function square(x) { return x * x };
 
 
function fmap(mixin, fn) {
	return function() {
		return mixin(fn.apply(null, arguments));
	}
}
 
 
 
var squareGen = fmap(square, gen);
 
console.log(squareGen()); // 1
console.log(squareGen()); // 4
console.log(squareGen()); // 9
console.log(squareGen()); // 16
 
 
 
function add(a, b) { 
    return a + b; 
}
 
 
var squareAdd = fmap(square, add);
console.log(squareAdd(2, 3)); // 25 = (2 + 3) ^ 2
console.log(squareAdd(5, 7)); // 144 = (5 + 7) ^ 2

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