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

Class template argument deduction

Before C++17, template argument deduction only worked for functions but not classes. This meant that when a class template had to be instantiated, all the template arguments had to be supplied. The following snippet shows several examples:

template <typename T>
struct wrapper
   T data;
std::pair<int, double> p{ 42, 42.0 };
std::vector<int>       v{ 1,2,3,4,5 };
wrapper<int>           w{ 42 };

By leveraging template argument deduction for function templates, some standard types feature helper functions that create an instance of the type without the need to explicitly specify template arguments. Such examples are std::make_pair for std::pair and std::make_unique for std::unique_ptr. These helper function templates, used in corroboration with the auto keyword, avoid the need for specifying template arguments for...