Programming with Types

Chapter 5. Function types

This chapter covers

• Simplifying the strategy pattern with function types
• Implementing a state machine without switch statements
• Implementing lazy values as lambdas
• Using the fundamental data processing algorithms map, filter, and reduce to reduce code duplication

We covered basic types and types built up from them. We also looked at how we can declare new types to increase the safety of our programs and enforce various constraints on their values. This is about as far as we can get with algebraic data types or the ability to combine types as sum types and product types.

The next feature of type systems we are going to cover, which unlocks a whole new world of expressiveness, is the ability to type functions. If ...