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haskell-training

Material for a Haskell training course

Haskell at work

The course proposes a practical approach to Haskell, a statically typed purely functional programming language. The course develops around the creation and evolution of a concrete project, highlighting where Haskell can help us to create a safe and maintainable application. It will contain the necessary theory and a lot of practice.

The course will introduce some more advanced concepts (e.g. type-level programming with Servant) but it would focus mostly on the day-to-day aspects of the language, which allow a programmer to become productive sooner.

Everything will be developed with the good practices of software engineering in mind.

Principles

Objectives

  • give the participants the feeling of how it is to work with Haskell
  • teach them the basics of Haskell development and how to solve practical problems
  • teach correct and precise data modelling using types
  • show them the best features of Haskell
  • provide directions on how to develop a real-world project
  • discuss shortcomings/limitations of the language

Target

  • professional developers
  • already experienced with some other programming language
  • possibly willing to use Haskell or FP concepts at work
  • interested in why Haskell is a good language for the industry
  • interested also in the practicalities

Buyers

  • single developers who want to get a practical approach to Haskell
  • companies interested in starting using Haskell
  • companies using Haskell wanting to train their junior developers

Prerequisites

  • a bit of software engineering experience
    • knowledge of what is required for a production system
  • already felt the pains of mutation and side effects management
  • some experience in other languages with basic FP concepts such as immutability and higher-order functions
  • basic Haskell syntax

Project

The course will unroll developing a simplified clone of a questionnaire app like Google Forms or Typeform.

It adapts well to the principles we stated above since:

  • it is extremely practical and concrete
  • allows to be modelled in simple way which still highlights the usage of algebraic data types
  • requires user interaction
  • requires persistence
  • requires definition of a web API

Outline

  • Chapter 1: Basic domain definition and terminal interaction
    • Haskell syntax and basic terminology
    • the value of types and purity
    • IO and side-effects
    • Chapter 2: Domain refinement and exposing a web API with Servant
      • defining a domain model guided by types
      • defining a web API specification using types
      • how to isolate the domain layer from persistence
      • functors and applicatives
    • Chapter 3: Adding persistence with PostgreSQL
      • describing a database schema in Haskell
      • writing composable queries
      • monads and monad transformers
    • Chapter 4: Testing and tooling
      • the easiness of writing unit tests
      • property based testing
      • doctests
      • mocks
    • Bonus chapter: Advanced type safety (to solve a concrete modelling problem)
      • GADTs
      • RankNTypes
      • Existential types

Length

The basic version of the course, without the bonus chapters, should take around two days, split in four chapters of ~ 4 hours each.

It could be enlarged to 3 days (6 chapters of ~ 4 hours each) adding the two bonus chapters

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Material for Haskell training

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