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

Chapter 6: Concepts and Constraints

The C++20 standard provides a series of significant improvements to template metaprogramming with concepts and constraints. A constraint is a modern way to define requirements on template parameters. A concept is a set of named constraints. Concepts provide several benefits to the traditional way of writing templates, mainly improved readability of code, better diagnostics, and reduced compilation times.

In this chapter, we will address the following topics:

  • Understanding the need for concepts
  • Defining concepts
  • Exploring requires expressions
  • Composing constraints
  • Learning about the ordering of templates with constraints
  • Constraining non-template member functions
  • Constraining class templates
  • Constraining variable templates and template aliases
  • Learning more ways to specify constraints
  • Using concepts to constrain auto parameters
  • Exploring the standard concepts library

By the end of this chapter...