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Template Metaprogramming with C++

You're reading from   Template Metaprogramming with C++ Learn everything about C++ templates and unlock the power of template metaprogramming

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Product type Paperback
Published in Aug 2022
Publisher Packt
ISBN-13 9781803243450
Length 480 pages
Edition 1st Edition
Languages
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Author (1):
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Marius Bancila Marius Bancila
Author Profile Icon Marius Bancila
Marius Bancila
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Table of Contents (16) Chapters Close

Preface 1. Part 1: Core Template Concepts
2. Chapter 1: An Introduction to Templates FREE CHAPTER 3. Chapter 2: Template Fundamentals 4. Chapter 3: Variadic Templates 5. Part 2: Advanced Template Features
6. Chapter 4: Advanced Template Concepts 7. Chapter 5: Type Traits and Conditional Compilation 8. Chapter 6: Concepts and Constraints 9. Part 3: Applied Templates
10. Chapter 7: Patterns and Idioms 11. Chapter 8: Ranges and Algorithms 12. Chapter 9: The Ranges Library 13. Assignment Answers 14. Other Books You May Enjoy Appendix: Closing Notes

Variadic variable templates

As mentioned before, variable templates may also be variadic. However, variables cannot be defined recursively, nor can they be specialized like class templates. Fold expressions, which simplify generating expressions from a variable number of arguments, are very handy for creating variadic variable templates.

In the following example, we define a variadic variable template called Sum that is initialized at compile-time with the sum of all integers supplied as non-type template arguments:

template <int... R>
constexpr int Sum = (... + R);
int main()
{
    std::cout << Sum<1> << '\n';
    std::cout << Sum<1,2> << '\n';
    std::cout << Sum<1,2,3,4,5> << '\n';
}

This is similar to the sum function written with the help of fold expressions. However, in that case, the numbers to add were provided as function...

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