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

Understanding the need for variadic templates

One of the most famous C and C++ functions is printf, which writes formatted output to the stdout standard output stream. There is actually a family of functions in the I/O library for writing formatted output, which also includes fprintf (which writes to a file stream), sprint, and snprintf (which write to a character buffer). These functions are similar because they take a string defining the output format and a variable number of arguments. The language, however, provides us with the means to write our own functions with variable numbers of arguments. Here is an example of a function that takes one or more arguments and returns the minimum value:

int min(int count, ...)
   va_list args;
   va_start(args, count);
   int val = va_arg(args, int);
   for (int i = 1; i < count; i++)
      int n = va_arg...