Book Image

Template Metaprogramming with C++

By : Marius Bancila
Book Image

Template Metaprogramming with C++

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

Defining alias templates

In C++, an alias is a name used to refer to a type that has been previously defined, whether a built-in type or a user-defined type. The primary purpose of aliases is to give shorter names to types that have a long name or provide semantically meaningful names for some types. This can be done either with a typedef declaration or with a using declaration (the latter was introduced in C++11). Here are several examples using typedef:

typedef int index_t;
typedef std::vector<
           std::pair<int, std::string>> NameValueList;
typedef int (*fn_ptr)(int, char);
template <typename T>
struct foo
   typedef T value_type;

In this example, index_t is an alias for int, NameValueList is an alias for std::vector<std::pair<int, std::string>>, while fn_ptr is an alias for the type of a pointer to a function that returns an int and has two parameters of type int...