dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Feb 16, 2009 at 12:11:42PM +0000, Garth N. Wells wrote:
> 
> 
> Anders Logg wrote:
> > On Mon, Feb 16, 2009 at 11:44:04AM +0000, Garth N. Wells wrote:
> >>
> >> Anders Logg wrote:
> >>> On Mon, Feb 16, 2009 at 11:30:46AM +0000, Garth N. Wells wrote:
> >>>> Anders Logg wrote:
> >>>>> On Mon, Feb 16, 2009 at 11:52:54AM +0100, Johan Hake wrote:
> >>>>>> On Monday 16 February 2009 11:31:36 Anders Logg wrote:
> >>>>>>> On Mon, Feb 16, 2009 at 10:12:21AM +0000, Garth N. Wells wrote:
> >>>>>>>> Anders Logg wrote:
> >>>>>>>>> On Mon, Feb 16, 2009 at 10:36:52AM +0100, Johan Hake wrote:
> >>>>>>>>>> On Sunday 15 February 2009 21:23:44 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:   5701:d3661203791d9c7707695c59adbbd3a2e20a220c
> >>>>>>>>>>> tag:         tip
> >>>>>>>>>>> user:        Anders Logg <logg@xxxxxxxxx>
> >>>>>>>>>>> date:        Sun Feb 15 21:23:36 2009 +0100
> >>>>>>>>>>> files:       dolfin/function/Function.cpp
> >>>>>>>>>>> description:
> >>>>>>>>>>> Move code from Function copy constructor to assignment operator and
> >>>>>>>>>>> call assignment operator from copy constructor
> >>>>>>>>>> I liked Garth solution better.
> >>>>>>>>>>
> >>>>>>>>>>  1) A copy constructor that, just copies the Function if it has
> >>>>>>>>>>     a FunctionSpace.
> >>>>>>>>>>  2) The assignment operator works only for discrete Functions.
> >>>>>>>>>>
> >>>>>>>>>> We could add an interpolate() (or something) function that
> >>>>>>>>>>
> >>>>>>>>>>   v.interpolate(*_vector, *_function_space);
> >>>>>>>>> We already have exactly such a function.
> >>>>>> Do we?
> >>>>> Yes:
> >>>>>
> >>>>>   /// Interpolate function to given function space
> >>>>>   void interpolate(GenericVector& coefficients, const FunctionSpace& V) const;
> >>>>>
> >>>>>>>>>> Then the user can explicitly create a discrete function of its
> >>>>>>>>>> user-defined Function. Now the user gets this as an implicitly result
> >>>>>>>>>> of a function copy, which make litle sense to me.
> >>>>>>>>>>
> >>>>>>>>>> But that's just me :)
> >>>>>>>>> I like it. Other opinions?
> >>>>>>>> It is neat, but I would prefer any interpolation to be more explicit so
> >>>>>>>> that it's clear what's going on. A copy should be a straight copy.
> >>>>>>>>
> >>>>>>>> Garth
> >>>>>>> ok. I've changed it back. See if it looks ok.
> >>>>>> Now a user cannot copy a Function that is not a discrete function, which was 
> >>>>>> the case before we started all this. 
> >>>>> Wasn't that the point? It's not possible to copy the eval() operator.
> >>>>>
> >>>> It is if a MyFunction object is copied to a MyFunction object, which we 
> >>>> couldn't do before. My change made this possible.
> >>>>
> >>>> Garth
> >>> What's the point of that? It's like copying half a Function.
> >>>
> >> No, it's a copy.
> > 
> > Only when assigning between two MyFunction objects.
> > 
> >>> If I do
> >>>
> >>>   v = w;
> >>>
> >>> I expect v to be in everything essential the same as w.
> >>>
> >> If you do
> >>
> >>    MyFuncion f0;
> >>    MyFunction f1 = f0;
> >>
> >> f0 and and f1 will be the same. The assignment operator is a separate story.
> > 
> > What if you do 
> > 
> >   MyFunction f0;
> >   MyOtherFunction f1 = f0;
> > 
> > ?
> > 
> 
> I expect that you'll get an error when you try to call eval().
> 
> Garth

Not if MyOtherFunction has overloaded eval(). So then f1 might be
cos(x) although f0 is sin(x).

So assignment from a user-defined function does not make sense unless
we interpolate.

If you just want to assign the FunctionSpace, then do

  MyOtherFunction f1(f0.function_space);

-- 
Anders

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