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

The decltype specifier

This specifier, introduced in C++11, returns the type of an expression. It is usually used in templates together with the auto specifier. Together, they can be used to declare the return type of a function template that depends on its template arguments, or the return type of a function that wraps another function and returns the result from executing the wrapped function.

The decltype specifier is not restricted for use in template code. It can be used with different expressions, and it yields different results based on the expression. The rules are as follows:

  1. If the expression is an identifier or a class member access, then the result is the type of the entity that is named by the expression. If the entity does not exist, or it is a function that has an overload set (more than one function with the same name exists), then the compiler will generate an error.
  2. If the expression is a function call or an overloaded operator function, then the result...