data-ts

Common algebraic structures heavily inspired by Haskell type classes adapted for fluent pointfree interfaces in Typescript. Strictly typed.

Source: The Typeclassopedia by Brent Yorgey

Install

yarn add data-ts

Import

import { Maybe } from 'data-ts';
/* or */
import * as Maybe from 'data-ts/lib/Maybe';

Run Test

$ yarn jest
$ yarn jest --watch

Publish

$ yarn publish

Instances

• Identity
• Maybe
• Either
• Task
• List
• Map
• Set
• Trie

Work in progress

• track 1:

  LazyMaybe
  

• track 2:

  ✅List -- Tree -- (BinaryTree) -- (BST) -- (Red-Black Tree)
                 \_ (Stack)
                 \_ (Map)
  

• track 3:

  Trie -- (RouteTrie)
  

• track 4:

  Monad2 -- (Either)
  

TODO Ideas

• create Functor2, Applicative2, Monad2 to support Either
• implement Alternative (.alt), Semigroup, Monoid, Foldable, Traversable
• implement the lazy version of Maybe, Either that apply multiple chains/maps per item
• implement naive, non-persistent (but immutable) versions of: (Linked)List, Stack, Tree, Dictionary (still useful for small inputs)
• implement persistent versions of: LinkedList, Stack, Tree, Dictionary
• see if it's possible to implement type Maybe<T> = Nothing | Just<T>; rather than type Maybe<T> = Nothing<T> | Just<T>;

References & Inspirations

• gcanti/fp-ts
• sanctuary-js
• evilsoft/crocks
• funkia/jabz
• origamitower/folktale
• ramda-fantasy
• fluture-js
• fantasy-land
• static-land

Note: this project does not implemented to be in compliant with Fantasyland but I draw a lot of inspiration from it. I however opt to be in consistent with Haskell interfaces but adapt it to be ergonomic in Typescript/Javascript.

Brain dump

• semigroup/monoid is useful because it allows you to implement pairwise funtions/operators and they will just work on your monoid (e.g. list). With associativity and that allows divide & conquer algorithms, parallelization, and incremental accumulation.
• function composition can be a monoid if the functions have the same type of input and output (endomorphism)
• hence, a monad is just a monoid in the category of endofunctors

A functor is a structure-preserving transformation between categories. It's some way to map objects from one category to objects of another category while also preserving the arrows between objects—think of it as a category homomorphism. ... An endofunctor is a functor from one category back to the same category. https://www.quora.com/What-is-an-endofunctor

fmap (haskell) can be viewed as fmap :: Functor f => (a -> b) -> (f a -> f b) which shows the preserved structor that maps from (a -> b) into (f a -> f b)