feat: initial commit

Author: baetheus

.gitignore

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+{
+  "deno.enable": true,
+  "editor.formatOnSave": true
+}

.vscode/settings.json

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+The MIT License (MIT)
+
+Copyright (c) 2018 Tom Crockett
+Copyright (c) 2019 Brandon Blaylock
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+

LICENSE

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+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import * as E from "./either.ts";
+
+// left
+// right
+// fold
+// isLeft
+// isRight
+// Monad
+// Foldable
+// Traversable

README.md

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+import { _0, _1 } from "./hkts.ts";
+import * as SL from "./type-classes.ts";
+
+/***************************************************************************************************
+ * @section Types
+ **************************************************************************************************/
+
+export type Left<L> = { tag: "Left"; left: L };
+export type Right<R> = { tag: "Right"; right: R };
+export type Either<L, R> = Left<L> | Right<R>;
+
+/***************************************************************************************************
+ * @section Constructors
+ **************************************************************************************************/
+
+export const left = <L>(left: L): Left<L> => ({ tag: "Left", left });
+export const right = <R>(right: R): Right<R> => ({ tag: "Right", right });
+
+/***************************************************************************************************
+ * @section Destructors
+ **************************************************************************************************/
+
+export const fold = <L, R, B>(
+  onLeft: (left: L) => B,
+  onRight: (right: R) => B
+) => (ma: Either<L, R>): B => {
+  switch (ma.tag) {
+    case "Left":
+      return onLeft(ma.left);
+    case "Right":
+      return onRight(ma.right);
+  }
+};
+
+/***************************************************************************************************
+ * @section Guards
+ **************************************************************************************************/
+
+export const isLeft = <L, R>(m: Either<L, R>): m is Left<L> => m.tag === "Left";
+export const isRight = <L, R>(m: Either<L, R>): m is Right<R> =>
+  m.tag === "Right";
+
+/***************************************************************************************************
+ * @section Instances
+ **************************************************************************************************/
+
+export const Monad = SL.createMonad2<Either<_0, _1>>({
+  of: (a) => right(a),
+  map: (fab, ta) => (isRight(ta) ? right(fab(ta.right)) : ta),
+  join: (tta) => (isRight(tta) ? tta.right : tta),
+});
+
+export const Foldable: SL.Foldable2<Either<_0, _1>> = {
+  reduce: (faba, a, tb) => (isRight(tb) ? faba(a, tb.right) : a),
+};
+
+export const Traversable: SL.Traversable2<Either<_0, _1>> = {
+  map: Monad.map,
+  reduce: Foldable.reduce,
+  traverse: (F, faub, ta) =>
+    isLeft(ta) ? F.of(left(ta.left)) : F.map(right, faub(ta.right)),
+};

either.test.ts

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+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import { compose, constant, flip, identity } from "./fns.ts";
+
+const a = {};
+const add = (a: number) => (b: number) => a + b;
+const addOne = add(1);
+const addTwo = add(2);
+
+Deno.test("identity", () => {
+  assertEquals(identity(a), a);
+});
+
+Deno.test("flip", () => {
+  assertEquals(flip(add)(1)(2), flip(add)(2)(1));
+});
+
+Deno.test("compose", () => {
+  assertEquals(compose(addOne)(addTwo)(0), 3);
+});
+
+Deno.test("constant", () => {
+  assertEquals(constant(a)(), a);
+});

either.ts

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+/***************************************************************************************************
+ * @section Types
+ **************************************************************************************************/
+
+export type Fn<AS extends unknown[], B> = (...as: AS) => B;
+
+/***************************************************************************************************
+ * @section Functions
+ **************************************************************************************************/
+
+export const curry2 = <A, B, C>(fn: (a: A, b: B) => C) => (a: A) => (b: B): C =>
+  fn(a, b);
+export const curry3 = <A, B, C, D>(fn: (a: A, b: B, c: C) => D) => (a: A) => (
+  b: B
+) => (c: C): D => fn(a, b, c);
+
+export const identity = <A>(a: A): A => a;
+
+export const flip = <A, B, C>(f: (a: A) => (b: B) => C) => (b: B) => (
+  a: A
+): C => f(a)(b);
+
+export const compose = <A, B>(fab: (a: A) => B) => <C>(fbc: (b: B) => C) => (
+  a: A
+): C => fbc(fab(a));
+
+export const constant = <A>(a: A) => () => a;

fns.test.ts

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+/***************************************************************************************************
+ * @section Hole Types
+ * @description Marks a type hole to be filled by the substitution ($) type
+ **************************************************************************************************/
+
+declare const index: unique symbol;
+
+export interface _<N extends number = 0> {
+  [index]: N;
+}
+export type _0 = _<0>;
+export type _1 = _<1>;
+export type _2 = _<2>;
+export type _3 = _<3>;
+export type _4 = _<4>;
+export type _5 = _<5>;
+export type _6 = _<6>;
+export type _7 = _<7>;
+export type _8 = _<8>;
+export type _9 = _<9>;
+
+/***************************************************************************************************
+ * @section Fixed Type
+ * @description Fixes a type so it is not replaced by the substitution ($) type
+ **************************************************************************************************/
+
+declare const fixed: unique symbol;
+
+export interface Fixed<T> {
+  [fixed]: T;
+}
+
+/***************************************************************************************************
+ * @section Substitution Type
+ * @description Replaces any type holes in a type with the supplied parameters
+ * @example
+ *     type FunctorFn<T> = <A, B>(fab: (a: A) => B, ta: $<T, [A]>) => $<T, [B]>;
+ *     type ArrayInstance = FunctorFn<Array<_>>;
+ *     // ArrayInstance = <A, B>(fab: (a: A) => B, ta: A[]): B[]
+ *     type RecordInstance = FunctorFn<{ value: _ }>;
+ *     // PromiseInstance = <A, B>(fab: (a: A) => B, ta: { value: A }): { value: B }
+ **************************************************************************************************/
+
+// prettier-ignore
+export type $<T, S extends any[]> = (
+  T extends Fixed<infer U> ? U :
+  T extends _<infer N> ? S[N] :
+  T extends any[] ? { [K in keyof T]: $<T[K], S> } :
+  T extends (...x: infer I) => infer O ? (...x: $<I, S>) => $<O, S> :
+  T extends object ? { [K in keyof T]: $<T[K], S> } :
+  T extends undefined | null | boolean | string | number ? T :
+  T
+);

fns.ts

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+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import * as O from "./option.ts";
+
+const addOne = (n: number) => n + 1;
+const someAddOne = O.some(addOne);
+const someNumber = O.some(2);
+const someOtherNumber = O.some(3);
+const onSome = addOne;
+const onNone = () => 100;