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

Parameter packs

A template or function parameter pack can accept zero, one, or more arguments. The standard does not specify any upper limit for the number of arguments, but in practice, compilers may have some. What the standard does is recommend minimum values for these limits but it does not require any compliance on them. These limits are as follows:

  • For a function parameter pack, the maximum number of arguments depends on the limit of arguments for a function call, which is recommended to be at least 256.
  • For a template parameter pack, the maximum number of arguments depends on the limit of template parameters, which is recommended to be at least 1,024.

The number of arguments in a parameter pack can be retrieved at compile time with the sizeof… operator. This operator returns a constexpr value of the std::size_t type. Let's see this at work in a couple of examples.

In the first example, the sizeof… operator is used to implement the end...