sfinae enabler

gistfile1.txt

/*
 * third.cpp
 * Date: 2012-11-01
 * Author: Karsten Ahnert (karsten.ahnert@gmx.de)
 */

#include <iostream>
#include <boost/utility/enable_if.hpp>

#define tab "\t"

using namespace std;

struct A { };

struct B { };

template< class T > struct is_a_or_b {};
template<> struct is_a_or_b< A > { const static bool value = true; };
template<> struct is_a_or_b< B > { const static bool value = true; };

template< class Class , class Enabler = void > struct dispatcher;

template< class T >
struct dispatcher< T , typename boost::enable_if_c< is_a_or_b< T >::value > ::type >
{
    const static size_t value = 2;
};

template<>
struct dispatcher< A >
{
    const static size_t value = 1;
};



int main( int argc , char *argv[] )
{
    cout << dispatcher< A >::value << endl;
    cout << dispatcher< B >::value << endl;
    return 0;
}