Re: Is there a way to span a suite of explicit instantiations automatically?

Avner wrote:


It is possible to instantiate the Foo class template over a pair of
type lists. For example:

     // class to instantiate over a set of types
     template <class T1, class T2>
     class Foo
     {
        T1 t1;
        T2 t2;
     };

     #include <tr1/tuple>

     using std::tr1::tuple;
     using std::tr1::tuple_size;
     using std::tr1::tuple_element;

     template < class T1, class T2,
                int N1 = tuple_size<T1>::value,
                int N2 = tuple_size<T2>::value >
     struct Instantiator
     {
         Foo< typename tuple_element<N1, T1>::type,
              typename tuple_element<N2, T2>::type> instance;

         // decrement second type parameter
         struct Instantiator<T1, T2, N1, N2-1> inner;
     };

     template <class T1, class T2, int N1>
     struct Instantiator<T1, T2, N1, 0>
     {
         Foo< typename tuple_element<N1, T1>::type,
              typename tuple_element<0, T2>::type> instance;

         // cycle second type parameter, decrement first
         struct Instantiator<T1, T2,
                             N1-1, tuple_size<T2>::value> inner;
     };

     template <class T1, class T2>
     struct Instantiator<T1, T2, 0, 0>
     {
         // terminate the iteration
         Foo< typename tuple_element<0, T1>::type,
              typename tuple_element<0, T2>::type> instance;
     };

     /*
         with T1, T2 having the following possibilities:

         T1 - unsigned char, short, unsigned short, long
         T2 - unsigned char, short, float, double
     */

     typedef tuple<unsigned char, short, unsigned short, long> T1Types;
     typedef tuple<unsigned char, short, float, double> T2Types;

     int main()
     {
         struct Instantiator< T1Types, T2Types > instantiation;

     }

Greg

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