Book Image

Modern C++ Programming Cookbook - Third Edition

By : Marius Bancila
Book Image

Modern C++ Programming Cookbook - Third Edition

By: Marius Bancila

Overview of this book

The updated third edition of Modern C++ Programming Cookbook addresses the latest features of C++23, such as the stack library, the expected and mdspan types, span buffers, formatting library improvements, and updates to the ranges library. It also gets into more C++20 topics not previously covered, such as sync output streams and source_location. The book is organized in the form of practical recipes covering a wide range of real-world problems. It gets into the details of all the core concepts of modern C++ programming, such as functions and classes, iterators and algorithms, streams and the file system, threading and concurrency, smart pointers and move semantics, and many others. You will cover the performance aspects of programming in depth, and learning to write fast and lean code with the help of best practices. You will explore useful patterns and the implementation of many idioms, including pimpl, named parameter, attorney-client, and the factory pattern. A chapter dedicated to unit testing introduces you to three of the most widely used libraries for C++: Boost.Test, Google Test, and Catch2. By the end of this modern C++ programming book, you will be able to effectively leverage the features and techniques of C++11/14/17/20/23 programming to enhance the performance, scalability, and efficiency of your applications.
Table of Contents (15 chapters)
13
Other Books You May Enjoy
14
Index

Using requires expressions and clauses

In the previous recipe, we introduced the topic of concepts and constraints, learning about them with the help of several examples that were solely based on already existing type traits. Moreover, we also used the terser syntax to specify concepts, with the concept name used instead of the typename or the class keyword in the template declaration. However, it is possible to define more complex concepts with the help of requires expressions. These are prvalues of the type bool that describe the constraints on some template arguments.

In this recipe, we will learn how to write requires expressions and an alternative way to specify constraints on template arguments.

Getting ready

The class template NumericalValue<T> and the function template wrap() defined in the previous recipe will be used in the code snippets presented in this recipe.

How to do it...

To specify requirements for template arguments, you can use requires...