Question

this code does not compile but i don’t why, also the typeid() function can take int as input parameter so the problem must be related to the template mechanism but i don’t get the rationale behind this fail.

#include <iostream>
#include <typeinfo>

template<typename T> void func(T)
{
  std::cout << typeid(T).name() << std::endl;
}

int main()
{
  func(int);  
  return(0);
}

What is wrong with this template/code ?

Answer 1

You need to pass an instance of type int, not the type itself:

func(int());
        ^^ note the parentheses

If you don’t want to pass an instance around, you could change your code like so:

#include <iostream>
#include <typeinfo>

template<typename T> void func()
{
  std::cout << typeid(T).name() << std::endl;
}

int main()
{
  func<int>();
  return(0);
}