zion

Zion

Fantasy Land compliant algebraic data types

General

Zion is a functional programming library inspired by Haskell and Fantasy Land.

It provides Haskell-like algebraic data-types and polymorphic functions against Fantasy Land algebraic structures.

Instalation & usage

npm install @totalsoft/zion

import List from "@totalsoft/zion/data/list";
import { $do } from "@totalsoft/zion";

Algebraic data types

Maybe

data  Maybe a  =  Nothing | Just a

Instance of:

• Setoid
• Ord
• Semigroup
• Monoid
• Functor
• Apply
• Applicative
• Alt
• Plus
• Foldable
• Traversable
• Chain
• ChainRec

List

data List a = Cons a (List a) | Nil

Instance of:

• Setoid
• Ord
• Semigroup
• Monoid
• Functor
• Apply
• Applicative
• Alt
• Plus
• Foldable
• Traversable
• Chain
• Extend

Map

data Map k a

Instance of:

• Setoid
• Semigroup
• Monoid
• Functor
• Foldable

KeyValuePair

data KeyValuePair k a

Instance of:

• Functor

Reader

data Reader r a

Instance of:

• Functor
• Apply
• Chain
• Contravariant
• Semigroup

Step

data Step b a

Instance of:

• Setoid
• Ord
• Functor
• Bifunctor

Polymorphic functions

• pure :: Applicative f => TypeRep f -> a -> f a
• contramap :: Contravariant f => (b -> a) -> f a -> f b
• fold :: Monoid m, Foldable f => (a -> m a) -> f a -> m a

Do notation

const monadSum = (monadX, monadY) =>
  $do(function*() {
    const x = yield monadX;
    const y = yield monadY;
    return x + y;
  })

expect(monadSum(Just(5), Just(6))).toStrictEqual(Just(11))
expect(monadSum(Just(5), Nothing)).toStrictEqual(Nothing)

expect(monadSum(List.fromArray([1]), List.fromArray([2]))).toStrictEqual(List.fromArray([1+2]))
expect(monadSum(List.fromArray([1, 2]), List.fromArray([3]))).toStrictEqual(List.fromArray([1 + 3, 2 + 3]))

expect(monadSum([1, 2], [3])).toStrictEqual([1 + 3, 2 + 3])
expect(monadSum([1], [2])).toStrictEqual([1 + 2])

expect(monadSum(x => x + 1, x => x - 1)(7)).toBe(7 + 1 + 7 - 1)
expect(monadSum(x => x * 2, x => x - 1)(5)).toBe(5 * 2 + 5 - 1)