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+// probably best not to *actually* use these, and instead check out
+//
+// https://folktale.origamitower.com/
+// https://ramdajs.com/
+// https://github.com/fantasyland
+
+// always :: a -> b -> a
+const always = curry((a, b) => a);
+
+// compose :: ((y -> z), (x -> y),  ..., (a -> b)) -> a -> z
+const compose = (...fns) => (...args) => fns.reduceRight((res, fn) => [fn.call(null, ...res)], args)[0];
+
+// curry :: ((a, b, ...) -> c) -> a -> b -> ... -> c
+function curry(fn) {
+  const arity = fn.length;
+
+  return function $curry(...args) {
+    if (args.length < arity) {
+      return $curry.bind(null, ...args);
+    }
+
+    return fn.call(null, ...args);
+  };
+}
+
+// either :: (a -> c) -> (b -> c) -> Either a b -> c
+const either = curry((f, g, e) => {
+  if (e.isLeft) {
+    return f(e.$value);
+  }
+
+  return g(e.$value);
+});
+
+// identity :: x -> x
+const identity = x => x;
+
+// inspect :: a -> String
+const inspect = (x) => {
+  if (x && typeof x.inspect === 'function') {
+    return x.inspect();
+  }
+
+  function inspectFn(f) {
+    return f.name ? f.name : f.toString();
+  }
+
+  function inspectTerm(t) {
+    switch (typeof t) {
+      case 'string':
+        return `'${t}'`;
+      case 'object': {
+        const ts = Object.keys(t).map(k => [k, inspect(t[k])]);
+        return `{${ts.map(kv => kv.join(': ')).join(', ')}}`;
+      }
+      default:
+        return String(t);
+    }
+  }
+
+  function inspectArgs(args) {
+    return Array.isArray(args) ? `[${args.map(inspect).join(', ')}]` : inspectTerm(args);
+  }
+
+  return (typeof x === 'function') ? inspectFn(x) : inspectArgs(x);
+};
+
+// left :: a -> Either a b
+const left = a => new Left(a);
+
+// liftA2 :: (Applicative f) => (a1 -> a2 -> b) -> f a1 -> f a2 -> f b
+const liftA2 = curry((fn, a1, a2) => a1.map(fn).ap(a2));
+
+// liftA3 :: (Applicative f) => (a1 -> a2 -> a3 -> b) -> f a1 -> f a2 -> f a3 -> f b
+const liftA3 = curry((fn, a1, a2, a3) => a1.map(fn).ap(a2).ap(a3));
+
+// maybe :: b -> (a -> b) -> Maybe a -> b
+const maybe = curry((v, f, m) => {
+  if (m.isNothing) {
+    return v;
+  }
+
+  return f(m.$value);
+});
+
+// nothing :: Maybe a
+const nothing = Maybe.of(null);
+
+// reject :: a -> Task a b
+const reject = a => Task.rejected(a);
+
+
+const createCompose = curry((F, G) => class Compose {
+  constructor(x) {
+    this.$value = x;
+  }
+
+  [util.inspect.custom]() {
+    return `Compose(${inspect(this.$value)})`;
+  }
+
+  // ----- Pointed (Compose F G)
+  static of(x) {
+    return new Compose(F(G(x)));
+  }
+
+  // ----- Functor (Compose F G)
+  map(fn) {
+    return new Compose(this.$value.map(x => x.map(fn)));
+  }
+
+  // ----- Applicative (Compose F G)
+  ap(f) {
+    return f.map(this.$value);
+  }
+});
+
+class Either {
+  constructor(x) {
+    this.$value = x;
+  }
+
+  // ----- Pointed (Either a)
+  static of(x) {
+    return new Right(x);
+  }
+}
+
+class Left extends Either {
+  get isLeft() {
+    return true;
+  }
+
+  get isRight() {
+    return false;
+  }
+
+  static of(x) {
+    throw new Error('`of` called on class Left (value) instead of Either (type)');
+  }
+
+  [util.inspect.custom]() {
+    return `Left(${inspect(this.$value)})`;
+  }
+
+  // ----- Functor (Either a)
+  map() {
+    return this;
+  }
+
+  // ----- Applicative (Either a)
+  ap() {
+    return this;
+  }
+
+  // ----- Monad (Either a)
+  chain() {
+    return this;
+  }
+
+  join() {
+    return this;
+  }
+
+  // ----- Traversable (Either a)
+  sequence(of) {
+    return of(this);
+  }
+
+  traverse(of, fn) {
+    return of(this);
+  }
+}
+
+class Right extends Either {
+  get isLeft() {
+    return false;
+  }
+
+  get isRight() {
+    return true;
+  }
+
+  static of(x) {
+    throw new Error('`of` called on class Right (value) instead of Either (type)');
+  }
+
+  [util.inspect.custom]() {
+    return `Right(${inspect(this.$value)})`;
+  }
+
+  // ----- Functor (Either a)
+  map(fn) {
+    return Either.of(fn(this.$value));
+  }
+
+  // ----- Applicative (Either a)
+  ap(f) {
+    return f.map(this.$value);
+  }
+
+  // ----- Monad (Either a)
+  chain(fn) {
+    return fn(this.$value);
+  }
+
+  join() {
+    return this.$value;
+  }
+
+  // ----- Traversable (Either a)
+  sequence(of) {
+    return this.traverse(of, identity);
+  }
+
+  traverse(of, fn) {
+    fn(this.$value).map(Either.of);
+  }
+}
+
+class Identity {
+  constructor(x) {
+    this.$value = x;
+  }
+
+  [util.inspect.custom]() {
+    return `Identity(${inspect(this.$value)})`;
+  }
+
+  // ----- Pointed Identity
+  static of(x) {
+    return new Identity(x);
+  }
+
+  // ----- Functor Identity
+  map(fn) {
+    return Identity.of(fn(this.$value));
+  }
+
+  // ----- Applicative Identity
+  ap(f) {
+    return f.map(this.$value);
+  }
+
+  // ----- Monad Identity
+  chain(fn) {
+    return this.map(fn).join();
+  }
+
+  join() {
+    return this.$value;
+  }
+
+  // ----- Traversable Identity
+  sequence(of) {
+    return this.traverse(of, identity);
+  }
+
+  traverse(of, fn) {
+    return fn(this.$value).map(Identity.of);
+  }
+}
+
+class IO {
+  constructor(fn) {
+    this.unsafePerformIO = fn;
+  }
+
+  [util.inspect.custom]() {
+    return 'IO(?)';
+  }
+
+  // ----- Pointed IO
+  static of(x) {
+    return new IO(() => x);
+  }
+
+  // ----- Functor IO
+  map(fn) {
+    return new IO(compose(fn, this.unsafePerformIO));
+  }
+
+  // ----- Applicative IO
+  ap(f) {
+    return this.chain(fn => f.map(fn));
+  }
+
+  // ----- Monad IO
+  chain(fn) {
+    return this.map(fn).join();
+  }
+
+  join() {
+    return new IO(() => this.unsafePerformIO().unsafePerformIO());
+  }
+}
+
+class List {
+  constructor(xs) {
+    this.$value = xs;
+  }
+
+  [util.inspect.custom]() {
+    return `List(${inspect(this.$value)})`;
+  }
+
+  concat(x) {
+    return new List(this.$value.concat(x));
+  }
+
+  // ----- Pointed List
+  static of(x) {
+    return new List([x]);
+  }
+
+  // ----- Functor List
+  map(fn) {
+    return new List(this.$value.map(fn));
+  }
+
+  // ----- Traversable List
+  sequence(of) {
+    return this.traverse(of, identity);
+  }
+
+  traverse(of, fn) {
+    return this.$value.reduce(
+      (f, a) => fn(a).map(b => bs => bs.concat(b)).ap(f),
+      of(new List([])),
+    );
+  }
+}
+
+class Map {
+  constructor(x) {
+    this.$value = x;
+  }
+
+  [util.inspect.custom]() {
+    return `Map(${inspect(this.$value)})`;
+  }
+
+  insert(k, v) {
+    const singleton = {};
+    singleton[k] = v;
+    return Map.of(Object.assign({}, this.$value, singleton));
+  }
+
+  reduceWithKeys(fn, zero) {
+    return Object.keys(this.$value)
+      .reduce((acc, k) => fn(acc, this.$value[k], k), zero);
+  }
+
+  // ----- Functor (Map a)
+  map(fn) {
+    return this.reduceWithKeys(
+      (m, v, k) => m.insert(k, fn(v)),
+      new Map({}),
+    );
+  }
+
+  // ----- Traversable (Map a)
+  sequence(of) {
+    return this.traverse(of, identity);
+  }
+
+  traverse(of, fn) {
+    return this.reduceWithKeys(
+      (f, a, k) => fn(a).map(b => m => m.insert(k, b)).ap(f),
+      of(new Map({})),
+    );
+  }
+}
+
+class Maybe {
+  get isNothing() {
+    return this.$value === null || this.$value === undefined;
+  }
+
+  get isJust() {
+    return !this.isNothing;
+  }
+
+  constructor(x) {
+    this.$value = x;
+  }
+
+  [util.inspect.custom]() {
+    return this.isNothing ? 'Nothing' : `Just(${inspect(this.$value)})`;
+  }
+
+  // ----- Pointed Maybe
+  static of(x) {
+    return new Maybe(x);
+  }
+
+  // ----- Functor Maybe
+  map(fn) {
+    return this.isNothing ? this : Maybe.of(fn(this.$value));
+  }
+
+  // ----- Applicative Maybe
+  ap(f) {
+    return this.isNothing ? this : f.map(this.$value);
+  }
+
+  // ----- Monad Maybe
+  chain(fn) {
+    return this.map(fn).join();
+  }
+
+  join() {
+    return this.isNothing ? this : this.$value;
+  }
+
+  // ----- Traversable Maybe
+  sequence(of) {
+    return this.traverse(of, identity);
+  }
+
+  traverse(of, fn) {
+    return this.isNothing ? of(this) : fn(this.$value).map(Maybe.of);
+  }
+}
+
+class Task {
+  constructor(fork) {
+    this.fork = fork;
+  }
+
+  [util.inspect.custom]() {
+    return 'Task(?)';
+  }
+
+  static rejected(x) {
+    return new Task((reject, _) => reject(x));
+  }
+
+  // ----- Pointed (Task a)
+  static of(x) {
+    return new Task((_, resolve) => resolve(x));
+  }
+
+  // ----- Functor (Task a)
+  map(fn) {
+    return new Task((reject, resolve) => this.fork(reject, compose(resolve, fn)));
+  }
+
+  // ----- Applicative (Task a)
+  ap(f) {
+    return this.chain(fn => f.map(fn));
+  }
+
+  // ----- Monad (Task a)
+  chain(fn) {
+    return new Task((reject, resolve) => this.fork(reject, x => fn(x).fork(reject, resolve)));
+  }
+
+  join() {
+    return this.chain(identity);
+  }
+}
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