Functional programing

• principles

  • functions
  • composition
  • types

• when to call language functional?

• supports

  1. function as first class concept
  2. immutability
  3. algebraic Data Types

• functions

  • Total or Partial
  • Pure or Impure

• Algebraic data type

  • map
  • flatMap / bind

• OOP equivalent pattern in FP

  • copy slides
  • Demo

The birthday greetings kata

A refactoring exercise to learn about dependency inversion and hexagonal architecture. Inspired by a blog post from Matteo Vaccari. You can find the original repo here.

Solution

I decided to solve the problem in a functional programming style using the Kotlin programming language and Arrow, a functional companion to the Kotlin standard library.

Resource

The following resources helped me in designing this solution:

• Functional and Reactive Domain Modeling
• Domain Modeling made functional
• Dependency rejection
• Self-contained example of testing with modules and Arrow FX