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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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Toc

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

Understanding friendship in templates

When you define a class, you can restrict access to its member data and member functions with the protected and private access specifiers. If a member is private, it can only be accessed within the class. If a member is protected, it can be accessed from derived classes with public or protected access. However, a class can grant access to its private or protected members to other functions or classes with the help of the friend keyword. These functions or classes, to which special access has been granted, are called friends. Let’s take a look at a simple example:

struct wrapper
{   
   wrapper(int const v) :value(v) {}
private:
   int value;
   friend void print(wrapper const & w);
};
void print(wrapper const& w)
{ std::cout << w.value << '\n'; }
wrapper w{ 42 };
print(w);

The wrapper class has a private data member called value. There is a free...

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