Function f

packages/typeclass/test/FlatMap.test.ts:26–26

(s: string)

  it("composeK", () => {
    const composeK = _.composeK(OptionInstances.FlatMap)
    const f = (s: string): O.Option<number> => s.length > 0 ? O.some(s.length) : O.none()
    const g = (n: number): O.Option<number> => n > 1 ? O.some(n) : O.none()
    const h = pipe(f, composeK(g))
    U.deepStrictEqual(h(""), O.none())