liftA2 fp-ts + Option example

liftA2.fp-ts.ts

import * as A from "fp-ts/lib/Applicative";
import { URIS, Kind } from "fp-ts/lib/HKT";
import { Option, option, some } from "fp-ts/lib/Option";

const lift = <F extends URIS, A, B, C>(
  F: A.Applicative1<F>,
  fn: (a: A) => (b: B) => C
) => (fa: Kind<F, A>) => (fb: Kind<F, B>): Kind<F, C> => {
  const fab = F.map(fa, fn);
  const c = F.ap(fab, fb);
  return c;
};

const liftToOption = <A, B, C>(fn: (a: A) => (b: B) => C) => (
  optionA: Option<A>
) => (optionB: Option<B>): Option<C> => {
  const optionAB = option.map(optionA, fn);
  const optionC = option.ap(optionAB, optionB);
  return optionC;
};

const add = (a: number) => (b: number) => a + b;
const optionAdd = lift(option, add);

add(1)(2);
optionAdd(some(1))(some(2));
liftToOption(add)(some(1))(some(2));