learn-by-doing course/tutorial for functional programming on scala
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.
project functors Dec 6, 2017
src merge Sep 12, 2018
.gitignore add gitignore Jan 18, 2018
.travis.yml merge answers Jan 8, 2018
Contributing.md add Contributing Jan 4, 2018
License add license Dec 28, 2017
Readme.md add IO Sep 12, 2018
build.sbt add nested and fix traversable Sep 12, 2018
example.gif optimize example.gif Jan 3, 2018


Learn Functional Programming course/tutorial on Scala Build Status Build Status


This course/tutorial was created with purpose to better understand functional programming idioms using Scala language. It covers type classes, monoids, functors, applicatives, monads, traversable/foldable, monad transformers, free monad.
Material is structured as set of stub/unimplemented functions/classes and tests for them. Your objective is to make all unit tests green. It is learn-by-doing course.

Example session

Example session


NICTA course was a great and interesting challenge for me to do in Haskell. I think Scala community will benefit from the similar course.

Target audience

The material in here is quite poor on theoretical/explanation part. I have tried to link material from other authors that I have found to be good into this course Readme to compensate for this. Some prior experience with functional idioms is recommended, but not necessary.

How to start

Just git clone this repository and follow steps in progression section. You can use any IDE and verify your results using sbt test. For me intellij works best - you can easily run individual tests out of it. In case if you got stuck - check answers branch.


It is important to keep the progression - a lot of things depend on each other. Implementing something = making all tests green for that thing.

Type classes


  • Observe general monoid pattern in learnfp/monoid/Monoid.scala
  • Implement learn-fp/src/main/scala/learnfp/monoid/ListMonoid.scala
  • Implement learn-fp/src/main/scala/learnfp/monoid/SimpleMonoid.scala
  • Implement learnfp/monoid/PairAdditiveMonoid.scala
  • Extra material:
    • Bartosz Milewski: Category Theory 3.1: Examples of categories, orders, monoids



  • Observe general monad pattern in learnfp/monad/Monad.scala
  • Implement learnfp/monad/Id.scala
  • Implement learnfp/monad/Maybe.scala
  • Implement learnfp/monad/List.scala
  • Implement learnfp/monad/Disjunction.scala
  • Implement learnfp/monad/Writer.scala
  • Implement learnfp/monad/State.scala
  • Extra material


  • Implement foldable in learnfp/foldable/Foldable.scala



  • Implement learnfp/traversable/Traversable.scala


  • Implement learnfp/nested/Nested.scala


  • Implement learnfp/nested/IO.scala

Monad Transformers

  • Observe general monad transformer typeclass in learnfp/transformer/MonadTransformer.scala
  • Implement learnfp/transformer/IdT.scala
  • Implement learnfp/transformer/MaybeT.scala
  • Implement learnfp/transformer/WriterT.scala
  • Implement learnfp/transformer/StateT.scala
  • Extra material:

Free monad

Contravariant functor

  • Observe general contravariant functor pattern in learnfp/contravariant/ContravariantFunctor.scala
  • Implement learnfp/contravariant/Show.scala
  • Implement learnfp/contravariant/Predicate.scala


  • Observe general comonad pattern in learnfp/comonad/CoMonad.scala
  • Implement learnfp/comonad/Id.scala
  • Implement learnfp/comonad/Env.scala


  • Implement Reader functor, monad, applicative and write unit tests for that
  • Implement ReaderT and write unit tests for that
  • Implement applicative for monad transformers
  • Implement applicative for Free

What was left out

  • Reader/ReaderT
  • Eff


In case if find a bug/issue - please report it to https://github.com/dehun/learn-fp/issues or e-mail me on yuriy.netesov@gmail.com
You also are very welcome to create PR.


  • Yuriy Netesov - initial implementation
  • Extra material references are owned by other authors