Book Image

Learn Type-Driven Development

By : Yawar Amin, Kamon Ayeva
Book Image

Learn Type-Driven Development

By: Yawar Amin, Kamon Ayeva

Overview of this book

Type-driven development is an approach that uses a static type system to achieve results including safety and efficiency. Types are used to express relationships and other assumptions directly in the code, and these assumptions are enforced by the compiler before the code is run. Learn Type-Driven Development covers how to use these type systems to check the logical consistency of your code. This book begins with the basic idea behind type-driven development. You’ll learn about values (or terms) and how they contrast with types. As you progress through the chapters, you’ll cover how to combine types and values inside modules and build structured types out of simpler ones. You’ll then understand how to express choices or alternatives directly in the type system using variants, polymorphic variants, and generalized algebraic data types. You’ll also get to grips with sum types, build sophisticated data types from generics, and explore functions that express change in the types of values. In the concluding chapters, you’ll cover advanced techniques for code reuse, such as parametric polymorphism and subtyping. By end of this book, you will have learned how to iterate through a type-driven process of solving coding problems using static types, together with dynamic behavior, to obtain more safety and speed.
Table of Contents (12 chapters)

Packaging Types and Values Together

ReasonML has fantastic support for the software engineering practice of dividing programs into small, modular components that can be swapped out for each other.

In this chapter, we will cover:

  • Modules and how they can be used to package types and values together
  • The difference between file modules and syntactic modules
  • Module signatures (both file and syntactic)
  • Using signatures to achieve information hiding
  • Using signatures to achieve type abstraction
  • Achieving zero-cost abstraction

Modules are groups of types and values accessible under a single name. This can be incredibly useful when you want to associate some types and operations together to make them easier to find and use together. They are kind of like namespaces in other languages, but more powerful because they can be composed in various ways.

Let's look at how to make some...