dolfin team mailing list archive

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

2008/4/3, Anders Logg <logg@xxxxxxxxx>:
> On Thu, Apr 03, 2008 at 10:21:04PM +0200, kent-and@xxxxxxxxx wrote:
>  > > 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).
>  > >
>  >
>  > Then I get a warning:
>  >
>  > cc1plus: warnings being treated as errors
>  > ./dolfin/la/GenericVector.h: In member function 'virtual const
>  > dolfin::GenericVector& dolfin::GenericVector::operator=(const
>  > dolfin::GenericVector&)':
>  > ./dolfin/la/GenericVector.h:111: warning: no return statement in function
>  > returning non-void
>  > scons: *** [dolfin/elements/ProjectionLibrary.os] Error 1
>  > scons: building terminated because of errors.
>
>
> Normally, one can trick the compiler by doing something like
>
>   return *(new GenericVector()); // code will never be reached
>
>  but this won't work here since GenericVector is not a concrete type so
>  it's not possible to instantiate it. And there are no other subclasses
>  to use since they should not be known to GenericVector...

Nothing wrong with the "return *this;" that was there.

--
Martin