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

C++20

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++

// templateTypeTraitsModifications.cpp

#include <iostream>
#include <type_traits>

int main(){

  std::cout << std::boolalpha << std::endl;

  std::cout << "std::is_const<std::add_const<int>::type>::value: " <<  std::is_const<std::add_const<int>::type>::value << std::endl;
  std::cout << "std::is_const<std::remove_const<const int>::type>::value: " << std::is_const<std::remove_const<const int>::type>::value << std::endl;

  std::cout << std::endl;
  typedef std::add_const<int>::type myConstInt;
  std::cout << "std::is_const<myConstInt>::value: " << std::is_const<myConstInt>::value << std::endl;
  typedef const int myConstInt2;
  std::cout << "std::is_same<myConstInt, myConstInt2>::value: " << std::is_same<myConstInt, myConstInt2>::value << std::endl;

  std::cout << std::endl;

  int fir= 1;
  int& refFir1= fir;
  using refToIntType= typename std::add_lvalue_reference<int>::type;
  refToIntType refFir2= fir;

  std::cout << "(fir, refFi1r, refFir2): "  << "(" << fir << ", " << refFir1 << ", " << refFir2 << ")" << std::endl;

  fir= 2;

  std::cout << "(fir, refFir1, refFir2): "  << "(" << fir << ", " << refFir1 << ", " << refFir2 << ")" << std::endl;

  std::cout << std::endl;

}


## Explanation 

Lines 10 and 11 determine at compile-time if the manipulated type is `const`. `myConstInt` is a type alias for an `const int`. Line 17 shows, with the help of the function `std::is_same`, that `myConstInt` and `myConstInt2` are the same types. An lvalue such as `fir` can only be bound to an `lvalue reference`. Line 24 shows this in a complicated way. Line 26 proves that `refFir1` and `refFire2` are references. 

Let's have a look at the solution to the previous exercise in this lesson.

Introduction

Basics

Details

Techniques

Design

Future

Conclusion

- Solution

Solution Review