Functional programming in TypeScript

Credits and sponsorship

This library was inspired by the following projects:

• fp-ts

A huge thanks to my sponsors who made the development of @fp-ts/core possible.

If you also want to become a sponsor to ensure this library continues to improve and receive maintenance, check out my GitHub Sponsors profile

Requirements

• TypeScript 4.8 or newer
• The strict flag enabled in your tsconfig.json file

{
  // ...
  "compilerOptions": {
    // ...
    "strict": true,
  }
}

Typed functional programming in TypeScript

This project represents the next major iteration of fp-ts and it's objective is a reconciliation with @effect in order to unify the ecosystems.

The @effect project will reduce it's scope to simply being an effect system and will delegate to fp-ts org all the lower level abstractions such as typeclasses and common data structures.

The objective of the fp-ts org in github and in npm (@fp-ts) is to simplify structure and management of the project, have smaller and better scoped packages.

Our "current" idea (that is well open for changes) is for fp-ts org to have:

• The @fp-ts/core library features a new implementation of the Higher Kinded Type (HKT) pattern, including common typeclasses such as Monad and widely-used data types like Option, Either, and ReadonlyArray
• @fp-ts/schema offers schema validation with static type inference, including decoders for data structures in @fp-ts/core and @effect/data
• @fp-ts/optic provides optics for structures in both @fp-ts/core and @effect/data

For those using fp-ts v2 and its ecosystem, roughly these are the equivalents:

• fp-ts -> @fp-ts/core + @effect/* packages
• io-ts -> @fp-ts/schema
• monocle-ts -> @fp-ts/optic

Note that @fp-ts/core will not contain any effect system (e.g. Task, TaskEither, ReaderTaskEither) since the handling of effects is entirely delegated to the packages contained in @effect/*.

Installation

To install the alpha version:

npm install @fp-ts/core

Warning. This package is primarily published to receive early feedback and for contributors, during this development phase we cannot guarantee the stability of the APIs, consider each release to contain breaking changes.

Documentation

• Guides (WIP)
  • Typeclass overview
  • Standard TypeScript types
  • Functional Error handling
    • The Option data type
    • The Either data type
• API Reference

License

The MIT License (MIT)