tut01-page03-example04.cc (flens/examples/tut01-page03-example04.cc)

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#include <flens/flens.cxx>

#include <iostream>

using namespace flens;

using namespace std;

///

/// In the `main` function we again start with a typedef for a `GeMatrix` with

/// elements of type `double` that are stored column-wise in memory.  Also,

/// we define a suitable range operator.

///

int

main()

{

    typedef FullStorage<double, ColMajor>  FS;

    typedef GeMatrix<FS>                   GeMatrix;

    const Underscore<GeMatrix::IndexType>  _;

///

/// Then we setup some matrix.

///

    GeMatrix  A(3,4);

    A = 1,  2,  3,  4,

        5,  6,  7,  8,

        9, 10, 11, 12;

    cout << "A = " << A << endl;

///

/// Matrix `B` is of type `const GeMatrix::View`.  So in particular this matrix

/// is in const context.

///

    const auto B = A(_(1,3),_);

///

/// Matrix `C` is of type `GeMatrix::ConstView` but it is *not* in const

/// context.

///

    auto C = B(_(1,3),_);

///

/// Matrix `D` would be of type `GeMatrix::View` and would reference a part

/// of a matrix of type `GeMatrix::ConstView`.  This would violate *const

/// correctness*.

    auto D = C(_(1,3),_);

    D(1,1) = 666;

    cout << "D = " << D << endl;

}