Passing Cell Obejct to self defined function

[Junxiang Wang]

Dear DEAL.II Communities,

I encountered the following compile error in the function interpolate(cell,beta) where I wanted to access cell data inside the function and failed to debug it after several methods....

"""

error: passing ‘const multiphyProblem<3>’ as ‘this’ argument discards qualifiers [-fpermissive]
 1018 |             double g_o = interpolate(cell,beta);

"""

The definition of  cell is:

""

   5       typename DoFHandler<dim>::active_cell_iterator cell = dof_handler
   4                                                               .begin_active(),
   3                                                      endc = dof_handler.end();

""

The definition of function interpolate() is:

"""

  13 template <int dim>
  12 double
  11 multiphyProblem<dim>::interpolate(TriaActiveIterator<dealii::DoFCellAccessor<dim, dim, false>>& cell, double      &beta)
  10 {
   9   double g{0};
   8
   7   double x = cell->center()[0] - 0.5;
   6   double y = cell->center()[1] - 0.5;
   5
   4   double r = std::sqrt(std::pow(x,2) + std::pow(y,2));
   3   // definition of g
   8
   9   return g;
  10
  11 }

"""

Do you know any issue may involved in the code? and can give me some hint.

Thanks a lot.

Best regard,

Junxiang Wang

[Daniel Arndt]

Junxiang Wang,

it looks like you are using a const multiphyProblem instance but its
member function interpolate is not const. Try

multiphyProblem<dim>::interpolate(TriaActiveIterator<dealii::DoFCellAccessor<dim,

dim, false>>& cell, double &beta) const

Best,
Daniel

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