fp-ts: Functional Programming in TypeScript

fp-ts is a TypeScript library providing tools for typed functional programming, including popular algebraic data types like `Option`, `Either`, `IO`, and `Task`, alongside type classes such as `Functor`, `Applicative`, and `Monad`. It uniquely implements Higher Kinded Types to enable robust functional patterns within TypeScript's type system. The current stable version is 2.16.11, last published approximately 8 months ago as of the current date. While actively maintained, recent announcements indicate that the `fp-ts` project is officially merging with the Effect-TS ecosystem, with Effect-TS being positioned as the successor, akin to `fp-ts v3`. This transition implies a future shift in development focus towards the Effect-TS project, offering enhanced capabilities and support for new users.