Re: [Boost-users] [uBLAS] iterator for matrix?

From: Lang Stefan (SLang_at_[hidden])
Date: 2008-03-11 12:26:58

You may be looking for the matrix storage container which you can access
via matrix<...>::data() like this:

    #include <boost/numeric/ublas/matrix.hpp>
    using namespace std;
    using namespace boost::numeric::ublas;
    matrix<double> m (3, 3);
    copy ( m.data().begin(), m.data().end(),
ostream_iterator<double>(cout, " ") );

Of course, if you have a sparse matrix, the number of elements
referenced by matrix::data() may be lower than the number of elements
your matrix normally should have. Also you have no control over the
order of elements: they may be stored by row, by column, or in yet
another way!

Cheers,
Stefan

> Date: Tue, 11 Mar 2008 14:25:58 +0800
> From: "Chung-Lin Wen" <jonathan.clwen_at_[hidden]>
> Subject: [Boost-users] [uBLAS] iterator for matrix?
> To: boost-users_at_[hidden]
> Message-ID:
> 	<eb7d82f30803102325w448b5a81w352bfa71a48b7258_at_[hidden]>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Hi,
> 
> It seems the ublas::matrix don't have begin() and end() that 
> the ordinary
> STL container would have.
> It do have begin1(), begin2(), end1(), end2(), but it only 
> traverse a row or
> a column.
> So, how could I use the iterators rather than hand-crafted for-loop to
> traverse the whole matrix?
> 
> e.g.,
> copy( matrix.begin(), matrix.end(),
>         ostream_iterator<element_type>(cout, " ") ) ; // ERROR: won't
> compile: matrix don't have begin & end
> 
> (I know matrix have overloaded the operator<<, it's only an example )