When a compiler can infer a template parameter?

Question

Sometimes it works sometimes not:

template  
void f(T t) {}

template 
class MyClass {
public:
  MyClass(T t) {}
};

void test          


        

Answer 1

In C++17, it is possible to infer some types using auto, though the template parameters still need to be specified here:

#include  
#include 

template    
auto print_stuff(T1 x, T2 y) 
{ 
    std::cout << x << std::endl;
    std::cout << y << std::endl;
}

int main() 
{ 
    print_stuff(3,"Hello!");
    print_stuff("Hello!",4);
    return 0; 
}

Using the -fconcepts flag in gcc, it is possible to infer the parameters, though this is not yet a part of the C++ standard:

#include  
#include 

auto print_stuff(auto x, auto y) 
{ 
    std::cout << x << std::endl;
    std::cout << y << std::endl;
}

int main() 
{ 
    print_stuff(3,"Hello!");
    print_stuff("Hello!",4);
    return 0; 
}