Re: [eigen] An insistent plea for an input operator

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

ok, my biggest objection was that getting general input right is hard,
and that we must then get the API right; but I can agree that in any
case we'll end up supporting the very simple stream format that your
operator>> is supporting. So, why not.

Others?

Benoit

2010/7/20 Helmut Jarausch <jarausch@xxxxxxxxxxxxxxxxxxx>:
> Hi,
>
> I know, I've asked for this feature several month, ago,
> but I'm obstinate to ask for it again and again.
>
> Background: I'm teaching C++ for beginners (mathematicians) and
> there should be an easy input operator for matrices and vectors.
>
> Currently, I have to patch Eigen (2 or 3) by adding
>
> namespace Eigen {
> template<typename Derived>
> std::istream & operator >>(std::istream & Inp, MatrixBase<Derived> & m)
> {
>  for (int i = 0; i < m.rows(); ++i)
>    for (int j = 0; j < m.cols(); j++)
>      Inp >> m(i,j);
>
>  return Inp;
> }
>
> }
>
> to make the following simple program run
>
>
> int main() {
> Eigen::MatrixXi A(2,3);
>  std::cerr << "intput 2x3 matrix:\n";
>  std::cin >> A;
>  std::cout << "I've got:\n" << A << std::endl;
> }
>
> I've never understood the objections against adding this.
> Pardon for being such obstinate,
> Helmut.
>
> My problem is, that students download Eigen themselves and forget about
> adding these few lines.
>
> --
> Helmut Jarausch
>
> Lehrstuhl fuer Numerische Mathematik
> RWTH - Aachen University
> D 52056 Aachen, Germany
>
>
>
>