Re: [ublas] Using constant matrices

From: Stefan Heinzmann (stefan_heinzmann_at_[hidden])
Date: 2006-10-31 11:55:53

Hi Gunter
--- Gunter Winkler <guwi17_at_[hidden]> wrote:
> Please have a look at:
> 
> http://freshmeat.net/projects/tvmet/ (fixed size lin.alg.)
>
http://www.bauv.unibw-muenchen.de/~winkler/ublas/examples/index.html
> (Ex3)

The second one seemed to be precisely what I need. There's a
problem with it, however. Here's my code:

static const double data[3][3] = {
    {65.481 , 128.553, 24.966 },
    {-37.797, -74.203, 112.   },
    {112.   , -93.786, -18.214}
};

{
    boost::numeric::ublas::matrix<double> xfm(3, 3);
    xfm = boost::numeric::ublas::make_matrix_from_pointer
              (3, 3, data[0]);
}

This produces a compiler error with VC++ 7.1:
error C2039: 'orientation_category' : is not a member of
'boost::numeric::ublas::readonly_array_adaptor<T>

> Can you create a small example which demonstrates this?

See above.

I've got an addition to propose to make storage adapters even
more convenient with C-style arrays:

/** \brief converts a C-style 2D array into a (readonly)
           usable dense matrix.
     *
     * <code>
     *   double data[5][10];
     *   vector<double> v(5);
     *   vector<double> x(10);
     *   matrix<double> m(5,10);
     *   v = prod(make_matrix_from_array(data), x);
     * </code>
     */
    template <class T, size_t M, size_t N>
    matrix<const T, readonly_array_adaptor<T> >
    make_matrix_from_array(const T (&array)[M][N])
    {
        typedef readonly_array_adaptor<T> a_t;
        typedef matrix<const T, a_t>      m_t;
        return m_t(M, N, a_t(M*N, array[0]));
    }

As you can see, the matrix size is inferred from the C-style
array.

Cheers
Stefan

                
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