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

11 Mentors

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

94 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.

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 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.
Avatar of Adrian King Legaspi

Adrian King Legaspi https://github.com/akilegaspi

Generally a Purely Functional Programming advocate and Professional Software Engineer in Scala/Haskell
Avatar of Simon Hafner

Simon Hafner https://github.com/reactormonk

type-driven development evangelist
Avatar of Nasy

Nasy Nasy Moe

I like Haskell very much. Although I'm not that good at it, I hope everyone will fall in love with her. I will do my best to help everyone. Besides, I come from China, so if you use Chinese, I can also understand it.
Avatar of Matthias Wimmer

Matthias Wimmer Matthias' Blog

Professionaly I do embedded programming in a mixture of C and Rust code. Coding in Clojure and 10+ years Java before. I couldn't apply Haskell directly at work so far, but feel how it influenced my way of programming in other languages as well.
Avatar of Frerich Raabe

Frerich Raabe https://github.com/frerich

I've been using Haskell on and off for the last eight years, and maintain a few Haskell packages. I believe knowing some Haskell makes you a better programmer in any other language and try to practice it whenever possible.
Fun. Challenging. Interesting

Community-sourced Haskell exercises

These are a few of the 94 exercises on the Haskell track. You can see all the exercises here.

Sieve
medium
number theory
math
Robot Name
medium
define type
io monad
random
List Ops
medium
accumulator strictness
library reimplementation
filtering
Resistor Color Duo
easy
strings
Rotational Cipher
medium
strings
Rail Fence Cipher
medium
algorithms
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.

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