Reason bindings vs TypeScript types

reselect.d.ts

export as namespace Reselect;

export type Selector<S, R> = (state: S) => R;

export type OutputSelector<S, R, C> = Selector<S, R> & {
  resultFunc: C;
  recomputations: () => number;
  resetRecomputations: () => number;
}
  
export function createSelector<S, R1, T>(
  selector: Selector<S, R1>,
  combiner: (res: R1) => T,
): OutputSelector<S, T, (res: R1) => T>;
export function createSelector<S, P, R1, T>(
  selector: ParametricSelector<S, P, R1>,
  combiner: (res: R1) => T,
): OutputParametricSelector<S, P, T, (res: R1) => T>;

export function createSelector<S, R1, R2, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  combiner: (res1: R1, res2: R2) => T,
): OutputSelector<S, T, (res1: R1, res2: R2) => T>;
export function createSelector<S, P, R1, R2, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  combiner: (res1: R1, res2: R2) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2) => T>;

export function createSelector<S, R1, R2, R3, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  combiner: (res1: R1, res2: R2, res3: R3) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3) => T>;
export function createSelector<S, P, R1, R2, R3, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  combiner: (res1: R1, res2: R2, res3: R3) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3) => T>;

export function createSelector<S, R1, R2, R3, R4, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  selector4: Selector<S, R4>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3, res4: R4) => T>;
export function createSelector<S, P, R1, R2, R3, R4, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  selector4: ParametricSelector<S, P, R4>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3, res4: R4) => T>;

export function createSelector<S, R1, R2, R3, R4, R5, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  selector4: Selector<S, R4>,
  selector5: Selector<S, R5>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5) => T>;
export function createSelector<S, P, R1, R2, R3, R4, R5, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  selector4: ParametricSelector<S, P, R4>,
  selector5: ParametricSelector<S, P, R5>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5) => T>;

export function createSelector<S, R1, R2, R3, R4, R5, R6, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  selector4: Selector<S, R4>,
  selector5: Selector<S, R5>,
  selector6: Selector<S, R6>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6) => T>;
export function createSelector<S, P, R1, R2, R3, R4, R5, R6, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  selector4: ParametricSelector<S, P, R4>,
  selector5: ParametricSelector<S, P, R5>,
  selector6: ParametricSelector<S, P, R6>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6) => T>;

export function createSelector<S, R1, R2, R3, R4, R5, R6, R7, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  selector4: Selector<S, R4>,
  selector5: Selector<S, R5>,
  selector6: Selector<S, R6>,
  selector7: Selector<S, R7>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7) => T>;
export function createSelector<S, P, R1, R2, R3, R4, R5, R6, R7, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  selector4: ParametricSelector<S, P, R4>,
  selector5: ParametricSelector<S, P, R5>,
  selector6: ParametricSelector<S, P, R6>,
  selector7: ParametricSelector<S, P, R7>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7) => T>;

export function createSelector<S, R1, R2, R3, R4, R5, R6, R7, R8, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  selector4: Selector<S, R4>,
  selector5: Selector<S, R5>,
  selector6: Selector<S, R6>,
  selector7: Selector<S, R7>,
  selector8: Selector<S, R8>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7, res8: R8) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7, res8: R8) => T>;
export function createSelector<S, P, R1, R2, R3, R4, R5, R6, R7, R8, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  selector4: ParametricSelector<S, P, R4>,
  selector5: ParametricSelector<S, P, R5>,
  selector6: ParametricSelector<S, P, R6>,
  selector7: ParametricSelector<S, P, R7>,
  selector8: ParametricSelector<S, P, R8>,
  combiner: (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7, res8: R8) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3, res4: R4, res5: R5, res6: R6,
            res7: R7, res8: R8) => T>;

Reselect.re

type selector('state, 'result) = 'state => 'result;

[@bs.module "reselect"]
external createSelector1:
  ('state => 'a, 'a => 'result) => selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector2:
  ('state => 'a, 'state => 'b, ('a, 'b) => 'result) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector3:
  ('state => 'a, 'state => 'b, 'state => 'c, ('a, 'b, 'c) => 'result) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector4:
  (
    'state => 'a,
    'state => 'b,
    'state => 'c,
    'state => 'd,
    ('a, 'b, 'c, 'd) => 'result
  ) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector5:
  (
    'state => 'a,
    'state => 'b,
    'state => 'c,
    'state => 'd,
    'state => 'e,
    ('a, 'b, 'c, 'd, 'e) => 'result
  ) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector6:
  (
    'state => 'a,
    'state => 'b,
    'state => 'c,
    'state => 'd,
    'state => 'e,
    'state => 'f,
    ('a, 'b, 'c, 'd, 'e, 'f) => 'result
  ) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector7:
  (
    'state => 'a,
    'state => 'b,
    'state => 'c,
    'state => 'd,
    'state => 'e,
    'state => 'f,
    'state => 'g,
    ('a, 'b, 'c, 'd, 'e, 'f, 'g) => 'result
  ) =>
  selector('state, 'result) =
  "createSelector";

[@bs.module "reselect"]
external createSelector8:
  (
    'state => 'a,
    'state => 'b,
    'state => 'c,
    'state => 'd,
    'state => 'e,
    'state => 'f,
    'state => 'g,
    'state => 'h,
    ('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h) => 'result
  ) =>
  selector('state, 'result) =
  "createSelector";

Just a comparison between writing bindings in Reason vs writing types in TypeScript.