curry.ts

interface CurriedFunction2<A, B, C> {
    (): CurriedFunction2<A, B, C>;
    (a: A): (b: B) => C;
    (a: A, b: B): C;
}

interface CurriedFunction3<A, B, C, D> {
    (): CurriedFunction3<A, B, C, D>;
    (a: A): CurriedFunction2<B, C, D>;
    (a: A, b: B): (c: C) => D;
    (a: A, b: B, c: C): D;
}

export function curry2<A, B, C>(f: (a: A, b: B) => C) {
    function curried(a: A, b: B) {
        switch (arguments.length) {
            case 0: return curried;
            case 1: return (b: B) => f(a, b);
            default: return f(a, b);
        }
    }

    return curried as CurriedFunction2<A, B, C>;
}

export function curry3<A, B, C, D>(f: (a: A, b: B, c: C) => D) {
    function curried(a: A, b: B, c: C): any {
        switch (arguments.length) {
            case 0: return curried;
            case 1: return curry2((_b: B, c: C) => f(a, b, c));
            case 2: return (c: C) => f(a, b, c);
            default: return f(a, b, c);
        }
    }
    return curried as CurriedFunction3<A, B, C, D>;
}