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QVM: Quaternions, Vectors, Matrices

vec_traits_defaults

#include <boost/qvm/vec_traits_defaults.hpp>

namespace boost
{
    namespace qvm
    {
        template <class VecType,class ScalarType,int Dim>
        struct vec_traits_defaults
        {
            typedef VecType vec_type;
            typedef ScalarType scalar_type;
            static int const dim=Dim;
        
            template <int I>
            static BOOST_QVM_INLINE_CRITICAL
            scalar_type write_element( vec_type const & x )
            {
                return vec_traits<vec_type>::template write_element<I>(const_cast<vec_type &>(x));
            }
        
            static BOOST_QVM_INLINE_CRITICAL
            scalar_type read_element_idx( int i, vec_type const & x )
            {
                return vec_traits<vec_type>::write_element_idx(i,const_cast<vec_type &>(x));
            }
        
            protected:
        
            static BOOST_QVM_INLINE_TRIVIAL
            scalar_type & write_element_idx( int i, vec_type & m )
            {
                /* unspecified */
            }
        };
    }
}

The vec_traits_defaults template is designed to be used as a public base for user-defined specializations of the vec_traits template, to easily define the required members. If it is used, the only member that must be defined by the user in a vec_traits specialization is write_element; the vec_traits_defaults base will define read_element, as well as scalar_type and dim automatically.

Optionally, the user may also define write_element_idx, in which case the vec_traits_defaults base will provide a suitable read_element_idx definition automatically. In addition, vec_traits_defaults defines a protected implementation of write_element_idx which may be made publicly available by the deriving vec_traits specialization in case the vector type for which it is being specialized can not be indexed efficiently. This write_element_idx function is less efficient (using meta-programming), implemented in terms of the required user-defined write_element.