Book Image

Learning D

By : Michael Parker
Book Image

Learning D

By: Michael Parker

Overview of this book

D is a modern programming language that is both powerful and efficient. It combines multiple paradigms in a way that opens up a whole new world of software design. It is used to develop both desktop and web applications, with future targets including mobile, and is available on multiple platforms. It is familiar to anyone with some experience in one or more of the C-family languages. However, hidden in the similarities are several differences that can be surprising when trying to apply common idioms from other languages. When learning D on your own, this can make it more time-consuming to master. In order to make the most of the language and become an idiomatic D programmer, it’s necessary to learn how to think in D. This book familiarizes you with D from the ground up, with a heavy focus on helping you to avoid surprises so that you can take your D knowledge to the next level more quickly and painlessly. Your journey begins with a taste of the language and the basics of compiling D programs with DMD, the reference D compiler developed by Digital Mars, and DUB, a community-developed build utility and package manager. You then set out on an exploration of major language features. This begins with the fundamentals of D, including built-in types, conditionals, loops and all of the basic building-blocks of a D program, followed by an examination of D’s object-oriented programming support. You’ll learn how these features differ from languages you may already be familiar with. Next up are D’s compile-time features, such as Compile-Time Function Evaluation and conditional compilation, then generic programming with templates. After that, you’ll learn the more advanced features of ranges and functional pipeline programming. To enhance your D experience, you are next taken on a tour of the D ecosystem and learn how to make D interact with C. Finally, you get a look at D web development using the vibe.d project and the book closes with some handy advice on where to go next.
Table of Contents (19 chapters)
Learning D
About the Author
About the Reviewers

Functional purity

The concept of functional purity was discussed briefly back in Chapter 7, Composing Functional Pipelines with Algorithms and Ranges. Now it's time for a quick introduction to functional purity as it is implemented in D. Consider the following function:

Vec2 add(Vec2 a, Vec2 b) pure {
  return Vec2(a.x + b.x, a.y + b.y);

Assuming that Vec2 is a struct and not a class, then this function is as pure as a function can be. No global state is mutated, no parameters are mutated, and given multiple calls with the same arguments, the result will be the same every time. Note that it has been marked with the pure attribute. With this, the compiler will produce an error if the function tries to modify any mutable static data (such as a module-scope variable) or if it calls any function not marked pure.

What the compiler does not do is prevent the modification of any reference variables, such as class instances, arrays or ref parameters. This, for example, is legal:

Vec2 add(ref Vec2...