Functor Composition with nullpub/hkts

compose.ts

import type { Kind, URIS } from "./hkt.ts";
import type * as TC from "./type_classes.ts";
import { flow, pipe } from "./fns.ts";

export type FunctorComposition<URI extends URIS, VRI extends URIS> = {
  readonly map: <A, I>(
    fai: (a: A) => I,
  ) => <B, C, D, E, F, G>(
    ta: Kind<URI, [Kind<VRI, [A, B, C, D]>, E, F, G]>,
  ) => Kind<URI, [Kind<VRI, [I, B, C, D]>, E, F, G]>;
};

export const getFunctorComposition = <URI extends URIS, VRI extends URIS>(
  U: TC.Functor<URI>,
  V: TC.Functor<VRI>,
): FunctorComposition<URI, VRI> => ({
  map: flow(V.map, U.map),
});

import * as E from "./either.ts";
import * as O from "./option.ts";

const t1 = getFunctorComposition(E.Functor, O.Functor);
const t2 = getFunctorComposition(O.Functor, E.Functor);

const f1 = (n: number) => n + 1;

const m1 = t1.map(f1);
const m2 = t2.map(f1);

const r1 = m1(E.right(O.some(1)));
const r2 = m1(E.left("asdf"));

const r3 = m2(O.some(E.right(1)));
const r4 = m2(O.none);
const r5 = m2(O.some(E.left("asdf")));

console.log({ r1, r2, r3, r4, r5 });

// {
//   r1: { tag: "Right", right: { tag: "Some", value: 2 } },
//   r2: { tag: "Left", left: "asdf" },
//   r3: { tag: "Some", value: { tag: "Right", right: 2 } },
//   r4: { tag: "None" },
//   r5: { tag: "Some", value: { tag: "Left", left: "asdf" } }
// }