Book Image

Template Metaprogramming with C++

By : Marius Bancila
5 (1)
Book Image

Template Metaprogramming with C++

5 (1)
By: Marius Bancila

Overview of this book

Learn how the metaprogramming technique enables you to create data structures and functions that allow computation to happen at compile time. With this book, you'll realize how templates help you avoid writing duplicate code and are key to creating generic libraries, such as the standard library or Boost, that can be used in a multitude of programs. The introductory chapters of this book will give you insights into the fundamentals of templates and metaprogramming. You'll then move on to practice writing complex templates and exploring advanced concepts such as template recursion, template argument deduction, forwarding references, type traits, and conditional compilation. Along the way, you'll learn how to write variadic templates and how to provide requirements to the template arguments with C++20 constraints and concepts. Finally, you'll apply your knowledge of C++ metaprogramming templates to implement various metaprogramming patterns and techniques. By the end of this book, you'll have learned how to write effective templates and implement metaprogramming in your everyday programming journey.
Table of Contents (16 chapters)
Part 1: Core Template Concepts
Part 2: Advanced Template Features
Part 3: Applied Templates
Appendix: Closing Notes

Defining class templates

Class templates are declared in a very similar manner, with the template keyword and the template parameter list preceding the class declaration. We saw the first example in the introductory chapter. The next snippet shows a class template called wrapper. It has a single template parameter, a type called T, that is used as the type for data members, parameters, and function return types:

template <typename T>
class wrapper
   wrapper(T const v): value(v)
   { }
   T const& get() const { return value; }
   T value;

As long as the class template is not used anywhere in your source code, the compiler will not generate code from it. For that to happen, the class template must be instantiated and all its parameters properly matched to arguments either explicitly, by the user, or implicitly, by the compiler. Examples for instantiating this class template are shown next...