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

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

I'm ok to add it, I cannot see how it could block us in the future to
support more sophisticated input format.

gael

On Tue, Jul 20, 2010 at 2:48 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> 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
>>
>>
>>
>>
>
>
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