dolfin team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/4/3, kent-and@xxxxxxxxx <kent-and@xxxxxxxxx>:
> > 2008/4/3, Anders Logg <logg@xxxxxxxxx>:
>  >> On Thu, Apr 03, 2008 at 07:47:13PM +0200, Martin Sandve Alnæs wrote:
>  >>  > We only talked about create() the other day, copy() can still be
>  >>  > useful! Or does the factory duplicate this functionality?
>  >>
>  >>
>  >> No, but Kent has added an assignment operator:
>  >>
>  >>   GenericVector* y = x.factory().createVector();
>  >>   *y = x;
>  >
>  > Ok, but the assignment operator doesn't exist in Python, so some
>  > variant of the copy function may still be needed. Could be just a
>  > wrapper for the two lines above.
>
>
>
> PyDolfin has assign:
>  dolfin_function_pre.i:%rename(assign) dolfin::Function::operator=;
>
>
>
>
>  >
>  > But the current default implementation of operator= (just return
>  > *this;) isn't good, it should be abstract or at least raise an error
>  > somehow.
>  >
>
>
> It did not compile when it was defined as an abstract function. But I
>  agree completely. You probably have a fix, I didn't manage.

I didn't know virtual operators were allowed at all in C++, but simply
calling dolfin_error in there is one solution (I do this in Python
some times to "simulate" pure virtual functions).


>  > And I the uBlas implementation seems potentially dangerous too,
>  >
>  > const uBlasVector& uBlasVector::operator= (const GenericVector& x_)
>  > {
>  >   const uBlasVector* x = dynamic_cast<const uBlasVector*>(&x_);
>  >   if (!x) error("The vector should be of type PETScVector");
>  >
>  >   *this = (*x)*1.0;
>  >   return *this;
>  > }
>  >
>  > In particular, this line
>  >   *this = (*x)*1.0;
>  > depends on (*x)*1.0 being resolved by the ublas_vector subclass,
>  > triggering operator= in ublas_vector. Implementing operator* in
>  > GenericVector will break this and possibly make an infinite recursion.
>  > Unless I misunderstand something? (I don't know ublas).
>  >
>
>
> Please help here as well. The reason it looks like this is that I don't
>  know ublas.
>
>  Kent

Plus the use of multiple inheritance... Maybe uBlasVector should be
changed to own an ublas_vector instead of being one? If operators are
added to GenericVector, multiple inheritance will be messy.

--
Martin