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Generic Programming Templates in C++

- Example

Explore how C++ automatically deduces function return types in templates by using decltype on argument expressions. Understand this technique through a practical example that adds two values and returns the correct summed type, preparing you for template metaprogramming challenges.

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Example: Automatic Template Return Type

C++
// 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;
}
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