tut01-page01-example4.cc (flens/examples/tut01-page01-example4.cc)

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#include <cxxstd/iostream.h>

#include <flens/flens.cxx>

using namespace flens;

using namespace std;

int

main()

{

    typedef GeMatrix<FullStorage<double, ColMajor> >      DGeMatrix;

    typedef DGeMatrix::ConstView                          DGeMatrixConstView;

    const Underscore<DGeMatrix::IndexType>  _;

    DGeMatrix  A(3,4);

    A = 1,  2,  3,  4,

        5,  6,  7,  8,

        9, 10, 11, 12;

    cout << "A = " << A << endl;

    ///

    ///  We want to create a const-view.  However, we do not declare `B` as

    ///  const.  Ideally the instantiation here would already cause a compile

    ///  time error.  You see next, why.

    ///

    DGeMatrixConstView  B = A(_(2,3),_);

    ///

    ///  `GeMatrix` implements two function operators for element access.  For

    ///  a const-view merely the read-only access must be allowed.  But as `B`

    ///  is not declared as const the read-write access gets called.

    ///

    cout << "B(1,1) = " << B(1,1) << endl;

}