Explore the power of C++ templates, from function and class basics to advanced features like instantiation and concepts, enhancing code flexibility, reusability, and abstraction without performance loss.

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C++17

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Templates are one of the many powerful features of Modern C++ programming. And with each new C++ standard, they become more important. 

Templates provide an efficient way to make your code more flexible and reusable, this way you can avoid repeating code that would otherwise be identical except for different types. Templates also give you the ability to provide abstraction without a performance penalty.

However, templates can be difficult to apply, can be counterintuitive, and have tricky error messages.

This course gives you the necessary information to overcome these hurdles and dive into the advanced topics. You’ll visit the basics such as function and class templates, and then explore the details to templates such as instantiation and fold expressions. Our journey also includes techniques based on templates, the design, and future directions of templates such as concepts. Based on this exhaustive tour of templates, a basic understanding of C++ is sufficient to master this course.

Let’s get started!

Generic Programming Templates in C++

# Example: Automatic Template Return Type

// templateAutomaticReturnType.cpp

#include <iostream>
#include <typeinfo>

template<typename T1, typename T2>
auto add(T1 first, T2 second) -> decltype(first + second){
  return first + second;
}

int main(){

  std::cout << std::endl;

  std::cout << "add(1, 1)= " << add(1,1) << std::endl;
  std::cout << "typeid(add(1, 1)).name()= " << typeid(add(1, 1)).name() << std::endl;

  std::cout << std::endl;

  std::cout << "add(1, 2.1)= " << add(1,2.1) << std::endl;
  std::cout << "typeid(add(1, 2.1)).name()= " << typeid(add(1, 2.1)).name() << std::endl;

  std::cout << std::endl;

  std::cout << "add(1000LL, 5)= " << add(1000LL,5) << std::endl;
  std::cout << "typeid(add(1000LL, 5)).name()= " << typeid(add(1000LL, 5)).name() << std::endl;

  std::cout << std::endl;
}

## Explanation

The example has a function `add` which takes two arguments and returns their sum. The return type of the function is deduced by the compiler by applying the `decltype` operator on the sum of the arguments. The expression `typeid(add(1, 2.1)).name()` such as in line 21 returns a string representation of the type of result. 

In this lesson, we'll look at an example of the automatic return type.

Introduction

Basics

Details

Techniques

Design

Future

Conclusion

- Example

Example: Automatic Template Return Type