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

Contract programming and unit tests

D has built-in support for contract programming and unit testing. D's contract programming implementation consists of two loosely related features: invariants and function contracts. None of these features would be as useful as they are without the assert expression.

Before we dig into the details, I'd like to point out that all of these features, except unit tests, are enabled by default. Passing -release to the compiler will disable asserts, function contracts, and invariants. Typically, you'll want to leave that flag out during development and use it when you are ready to start testing the release version.

Assert contracts

The assert expression evaluates a Boolean expression and throws an AssertError when the result is false. The basic syntax takes two forms:

assert(10 == 10);
assert(1 > 0, "You've done the impossible!");

Both of these examples will always evaluate to true since the Boolean expressions use constants. If the second one did somehow fail...