dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Oct 26, 2008 at 12:03:27AM +0200, Anders Logg wrote:
> On Sat, Oct 25, 2008 at 11:17:15PM +0200, DOLFIN wrote:
> > One or more new changesets pushed to the primary dolfin repository.
> > A short summary of the last three changesets is included below.
> > 
> > changeset:   4993:01188514d401addaa869e7c99acc87dce6889f3b
> > tag:         tip
> > user:        "Garth N. Wells <gnw20@xxxxxxxxx>"
> > date:        Sat Oct 25 22:17:05 2008 +0100
> > files:       dolfin/fem/UFCCell.h
> > description:
> > Use const_cast to get UFCCell to compile.
> > 
> > Should ufc::cell::entity_indices and ufc::cell::coordinates be
> > 
> >   unsigned int const** and
> > 
> >   double const**
> > 
> > ?
> 
> Yes, it looks like we've made a mistake in UFC.h. I found the
> following uses of "const" and "*" in UFC.h:

Sorry, this is obviously completely wrong! I took a closer look at
what the position of "const" means. It should indeed by

  const double*

which means that the objects pointed to (the values in the array) are
const.

In the case with ufc::cell::coordinates and ufc::cell::entity_indices,
it would be difficult to insert any const since that would prevent
users from copying values into the ufc::cell data structures. We might
also need to do that (rather than set the pointer to point to the data
in the DOLFIN mesh).

-- 
Anders


> 1. const double* coordinates
> 
> This should really be
> 
>   double* const coordinates
> 
> This means that the function promises not to change the values in the
> coordinates array, which is what we want. The way we do it now is that
> we promise not to change the pointer, which has no meaning since the
> pointer is passed by value and changing that copied pointer inside the
> function does not modify the pointer passed to the function.
> 
> 2. const double* dof_values
> 
> Same here.
> 
> 3. const double * const * w
> 
> This should really be
> 
>   double * const * const w
> 
> meaning that we don't change the arrays pointed to and not the values
> in those arrays.
> 
> 4. const char* signature() const = 0;
> 
> Why don't we use std::string here?
> 
> Can we change this in UFC? It's needed for const-correctness in DOLFIN
> (and other codes that may use UFC).
> 
> Martin?
> 



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