Question

Possible Duplicate:
C++ Restrict Template Function
Is it possible to write a C++ template to check for a function's existence?

Is it possible to restrict the types for which a template may be instantiated
(that is, have a compiler error if I use template<type_not_allowed>)?

Answer 1

One way would be to provide no default implementation, and specialize your class template only on those types you wish to allow. For example:

#include <iostream>
using namespace std;

template<class X> class Gizmo
{
public:
    Gizmo();
};

template<> Gizmo<int>::Gizmo()
{
}

int main()
{
    Gizmo<float> gf; // ERROR:  No specialization for Gizmo<float> results in a linking error
}