pipeline.ts

function identity(x) {
	return x;
}

function fp<T1, T2> (
	transform: (x: T1) => T2
	): (x: T1) => T2;

function fp<T1, T2, T3> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3
	): (x: T1) => T3;

function fp<T1, T2, T3, T4> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4
	): (x: T1) => T4;

function fp<T1, T2, T3, T4, T5> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5
	): (x: T1) => T5;

function fp<T1, T2, T3, T4, T5> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5
	): (x: T1) => T5;

function fp<T1, T2, T3, T4, T5, T6> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5,
	transform5: (x: T5) => T6
	): (x: T1) => T6;

function fp<T1, T2, T3, T4, T5, T6, T7> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5,
	transform5: (x: T5) => T6,
	transform6: (x: T6) => T7
	): (x: T1) => T7;

function fp<T1, T2, T3, T4, T5, T6, T7, T8> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5,
	transform5: (x: T5) => T6,
	transform6: (x: T6) => T7,
	transform7: (x: T7) => T8
	): (x: T1) => T8;

function fp<T1, T2, T3, T4, T5, T6, T7, T8, T9> (
	transform1: (x: T1) => T2,
	transform2: (x: T2) => T3,
	transform3: (x: T3) => T4,
	transform4: (x: T4) => T5,
	transform5: (x: T5) => T6,
	transform6: (x: T6) => T7,
	transform7: (x: T7) => T8,
	transform8: (x: T8) => T9
	): (x: T1) => T9;
function fp(...transforms: Array<(x: any) => any>) {
	switch (transforms.length) {
	case 0: return identity;
	case 1:
		let transform = transforms[0];
		return transform;
	case 2:
		let transform0 = transforms[0];
		let transform1 = transforms[1];
		return (value) => transform1(transform0(value))
	default:
		return (value) => {
			let data = value;
			for(let i = 0, len = transforms.length; i < len; i++) {
				data = transform(data);
			}
			return data;
		}
	}
}