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Haskell

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Haskell is a functional programming language which is pure and statically-typed. It's known for lazy evaluation, where evaluation is deferred until necessary, and its purity, where monads are used for working with side-effects.
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Track mentors

17 Mentors

Our mentors are friendly, experienced Haskell developers who will help teach you new techniques and tricks.
Track students

12,818 Students

Join thousands of students who have enjoyed learning and improving their skills by taking this track.
Track exercises

96 Exercises

Hundreds of hours have gone into making these exercises fun, useful, and challenging to help you enjoy learning.

About Haskell

{-# LANGUAGE OverloadedStrings #-}
module Main (main) where
import Web.Scotty

main = scotty 3000 $
  get "/:who" $ do
    who <- param "who"
    text $
      "Beam " <> who <> " up, Scotty!"

Haskell is a general-purpose programming language known for being purely functional, non-strict with strong static typing and for having type inference.

Purely functional means that you don't update variables or modify state. Pure functions will always return the same value given the same input and will do nothing else. Functions that are referentially transparent are more predictable and more composable. Non-strict (somewhat like lazy) means that you can express infinite data structures. Strong static typing means that a lot of program errors are caught during compilation. Type inference means that the compiler can often figure out the type of a value by itself. The compiler can also tell you if a value has conflicting types in different parts of the code.

There are more than 10,000 free third-party packages available at Hackage, the Haskell community's central package archive, and you can download them using the Stack tool that Exercism also uses.

You can also read the free book Learn You a Haskell for Great Good or follow the interactive tutorial at tryhaskell.org.

Join the Haskell track

To me, the standout track has been the Haskell track.

With only a very limited grasp of functional programming, the frequent and insightful comments I received were invaluable in getting to know the language.

Erik Schierboom, Arnhem
Relaxed. Encouraging. Supportive.

Meet the Haskell Track mentors

Once you join the Haskell language track, you will receive support and feedback from our team of mentors. Here are the bios of a few of the mentors of this track.

Avatar of Antoine Leblanc

Antoine Leblanc https://github.com/nicuveo

The one thing I enjoy more than writing Haskell is sharing the joy! I have worked in the past on teaching it to beginners, with the explicit goal of demystifying it; mentoring was the logical next step.
Avatar of Brooks J Rady

Brooks J Rady thelostlambda.xyz

Writing in Haskell isn't just a new syntax, it's a new mindset. It provides learners with a way to rediscover the beauty in programming.
Avatar of Daniel Brice

Daniel Brice https://github.com/friedbrice

I use Haskell at work because it allows me to rapidly deliver easily-maintainable applications with a high degree of confidence in their correctness.
Avatar of Mats Rauhala

Mats Rauhala https://github.com/MasseR

Working with Haskell at work for the past couple of years. Before that a Haskell hobbyist for 10 or so years.
Avatar of Bhavik Mehta

Bhavik Mehta https://github.com/b-mehta

I love functional programming, especially the deep theoretical background that comes with Haskell as well as the readability and safety it provides.
Avatar of Peter Tillemans

Peter Tillemans https://github.com/ptillemans

I am an electronics engineer and language geek who learned programming on an hp-41 and C-64. Now I do mostly java, javascript, python, rust and haskell. I believe that code should sing its intent so the last row in the hall understands the last syllable.
Fun. Challenging. Interesting

Community-sourced Haskell exercises

These are a few of the 96 exercises on the Haskell track. You can see all the exercises here.

List Ops
medium
accumulator strictness
library reimplementation
filtering
Robot Name
medium
define type
io monad
random
Grade School
easy
define type
Alphametics
medium
maybe
Acronym
easy
strings
Pig Latin
medium
strings
Passionate. Knowledgeable. Creative.

Meet the Haskell Track maintainers

The Haskell Maintainers are the brains behind the Haskell Track. They spend their spare time creating interesting and challenging exercises that we can all learn from. We are incredibly grateful for their hard work. Here are the bios of a few of the maintainers of this track.

Avatar of Peter Tseng

Peter Tseng

I taught myself Haskell as a logical next step after having learned OCaml. Although I don't use it for my job, I find it an interesting language; I especially enjoy its type system. I'm mostly a "break glass in case of emergency" maintainer.
Avatar of Simon Shine

Simon Shine https://simonshine.dk

I've been a classroom teacher in compilers and various functional languages for five years. Having pure functions and isolation of side-effects are fundamental to separation of concerns. Strong, static types, type inference and algebraic types are hard for me to live without.

Get started with the Haskell track. As with everything on Exercism, it's 100% free!

Join the Haskell Track