C++ Fundamentals for Professionals/

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- Example

- Example

Here, we'll see an example of how decltype can be used to automatically deduce the return type of a function.

We'll cover the following...

The add function #

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#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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