FIO is a type-safe, purely functional effect system for F#, designed for building highly concurrent and asynchronous applications. It provides a lightweight DSL for writing composable programs using functional effects.

Inspired by ZIO and Cats Effect, FIO features:

• An IO monad for managing side effects
• Fibers (green threads) for scalable concurrency
• A focus on purity, type safety, and performance

FIO was developed as part of a master’s thesis in Computer Science at DTU.

Compose functional effects with FIO:

module FIOAppUsage

open FSharp.FIO.DSL
open FSharp.FIO.Lib.IO
open FSharp.FIO.App

type WelcomeApp() =
    inherit FIOApp<unit, exn> ()

    override _.effect = fio {
        do! FConsole.PrintLine "Hello! What is your name?"
        let! name = FConsole.ReadLine ()
        do! FConsole.PrintLine $"Hello, %s{name}! Welcome to FIO! 🪻💜"
    }

WelcomeApp().Run()

Check out the repository for more information.