dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

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.

Well it is but then it would be necessary to keep a pointer to the
given Function and propagate the eval call to that Function's eval.
That seems a bit overkill.

> Also sometimes a copy is something different than an assignment, so it is not 
> always meaningfull to use *this = other; in the copy constructor.

I've found it's almost always the case that one can implement the
copy constructor by

  *this = other;

We use this in a bunch of other places, including the Mesh class.

In which cases will it break?

-- 
Anders

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