[petsc-dev] declaring argument as const basic type in PETSc

[Barry Smith]

On Aug 17, 2011, at 1:37 PM, Dmitry Karpeev wrote:

> Okay. By "typo" I meant that I never intended to have a "const
> PetscInt" argument.
> It just got contaminated from the nearby "const PetscInt *".
> I'm not sure what meaning "const PetscInt" would have, since C has
> pass-by-value
> semantics, but I'm not sure whether some C-subtlety might be at play here.

   Dmitry,

   Ok, I'll fix yours.

   But someone else has done as well I think :-)

   Barry

> 
> On Wed, Aug 17, 2011 at 10:34 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>> 
>> On Aug 17, 2011, at 1:31 PM, Dmitry Karpeev wrote:
>> 
>>> That's just a typo on my part.
>>> I'm rewriting the whole SA ball of wax, but I can push a quicker fix
>>> for this too,
>> 
>>   What do you mean typo? I fixed the repository so that the declaration and the prototype match. You don't need to do anything.
>> 
>>   But my question remains, should we const declare function arguments?
>> 
>>  barry
>> 
>>> but, unfortunately, I won't be able to do that untill next Monday.
>>> 
>>> 
>>> Dmitry.
>>> 
>>> On Wed, Aug 17, 2011 at 10:09 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>> 
>>>>   Some declarations of the form
>>>> 
>>>> extern PetscErrorCode SAAddData(SA arr, const PetscInt len, const PetscInt *ia, const PetscScalar *wa, const PetscInt *ja);
>>>> 
>>>> have crept into PETSc.  const PetscInt len
>>>> 
>>>> Do we want to have such beasties? What purpose do they serve?
>>>> 
>>>> My understanding is that it is contaminating the entire code (because of the extern PetscErrorCode SAAddData(SA arr, const PetscInt len, const PetscInt *ia, const PetscScalar *wa, const PetscInt *ja); with the knowledge that internally the subroutine never changes the value of the stack variable function which is the opposite of encapsulation. What am I missing? Is this just stupid C syntax, is there a better way?
>>>> 
>>>>   Thanks
>>>> 
>>>>    Barry
>>>> 
>>>> 
>> 
>>