Mastering Functional Programming

Effect Types - Abstracting Away Side Effects

In the previous chapter, we saw why side effects may be a source of trouble. We also briefly discussed effect types. Effect types are a technique of functional programming that allow for the abstraction of side effects.

In this chapter, we will have a look at how this works. We will learn the philosophy behind the pattern. Also, we will see how to sequentially combine side effects trapped in effect types.

In this chapter, we will cover the following topics:

• Turning effects into data
• The sequential combination of effect types with Monads – the map and flatMap functions