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Help with some template code

Started by Rebooted Jan 29, 2006 at 9:35 AM 1 replies 2.2k views

Original Post

Jan 29, 2006 at 9:35 AM

The following code is giving me this error with Visual C++ 8: C3860: template argument list following class template name must list parameters in the order used in template parameter list.


template <size_t dimensions, typename T> struct Vector
{
    BOOST_STATIC_ASSERT( (dimensions >= 2) && (dimensions <= 4) );
};

class VectorMembers
{
    public:

        static T& Get(Vector<dimensions, T> &v, size_t i)
        {
            return v.*members;
        }

    private:

        typedef T Vector<dimensions, T>::* const vec[dimensions];

        static const vec members;
};

template <typename T> struct Vector<2, T>
{
    T x, y;
};

template< typename T >
const typename VectorMembers<2, T>::vec VectorMembers<2, T>::members = { &Vector<2, T>::x, &Vector<2, T>::y };

The problem is with initilizing the static member of VectorMembers. I need to do this slightly differently to get the compiler to do what I want, but I don't know how. Thanks for any help.

MaulingMonkey

Jan 29, 2006 at 9:54 AM

You're trying to partially specialize the static member without partially specializing the class it belongs to. Getting these to align seems to get things working on G++:

template <size_t dimensions, typename T> struct Vector{    BOOST_STATIC_ASSERT( (dimensions >= 2) && (dimensions <= 4) );};template <size_t dimensions, typename T> class VectorMembers;template < typename T > class VectorMembers<2, T>{    public:        static T& Get(Vector<2, T> &v, size_t i)        {            return v.*members;        }    private:        typedef T Vector<2, T>::* const vec[2];        static const vec members;};template <typename T> struct Vector<2, T>{    T x, y;};template< typename T >const typename VectorMembers<2, T>::vec VectorMembers<2, T>::members = { &Vector<2, T>::x, &Vector<2, T>::y };

Instead of this, I'd recommend moving the partial specialization into VectorMembersBase - e.g.:

template < size_t dimensions , typename T > class VectorMembersBase;template < typename T > class VectorMembersBase< 2 , T > {protected:        typedef T Vector<2, T>::* const vec[2];        static const vec members;};template< typename T >const typename VectorMembersBase<2, T>::vec VectorMembersBase<2, T>::members = { &Vector<2, T>::x, &Vector<2, T>::y };//VectorMembersBase< 3 , T >//VectorMembersBase< 4 , T >//VectorMembersBase< N , T >template < size_t dimensions , typename T > class VectorMembers< dimensions , T > : public VectorMembersBase< dimensions , T > {    ...Get implementation...}

Rebooted

Jan 29, 2006 at 10:22 AM

Thank you, the second method works perfectly.

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