anastasiial/flatten

Examples and exercises with monad transformers

Flatten your code

This project is a hands-on tutorial with exercises and answers, that teaches how to flatten stacked containers like Future[Option[A]] so that they can be used in for-comprehensions.

There's an accompanying presentation: https://speakerdeck.com/eamelink/flatten-your-code

Prerequisites

• Some Scala experience
• Frustration with deeply nested map and flatMap structures.

Usage

Most of the code is not runnable: we only rely on the typechecker. That means it's critical to look at the code in an IDE (or ENSIME) that can show you the type of values.

Structure

There are two sbt projects: basics and play-specific.

The first 14 parts are in basics. There is a package flatten with the tutorial and exercises, and a package answers with answers to the exercises.

The final 3 parts are in the controllers package of play-specific.

ToC

• Parts 1-5 introduce for-comprehensions.
• Parts 6 and 7 deal with nested containers.
• Parts 8-12 generalize the concept from part 7. These parts are optional, you can safely skip to part 13.
• Parts 13 and 14 continue with nested containers.
• Parts 15 to 17 show the concepts in a Play context.

Scalaz documentation

You can find Scalaz documentation on the http://docs.typelevel.org/