On Thu, Nov 20, 2014 at 02:27:46PM +0100, Martin Sandve Alnæs wrote:

> How do you use it from user code?

If I do something like this (in C++):

    Scalar m;
    Assembler assembler;
    assembler.assemble(m, M); // M is a functional
    cout << "Value is m = " << sqrt(m) << endl;

> It's important now to call apply before
> extracting the value. Some times breaking code is better than a
> silent behaviour change...

Yes, but not silently breaking user code... ;-)

get_scalar_value seems to me just a different name for operator double().

I think we should have both, since we have had operator double()
before. Are there any objections to add it back? It can just call
get_scalar_value().

-- 
Anders


>
> Martin
>
> On 20 November 2014 14:23, Martin Sandve Alnæs <marti...@simula.no> wrote:
>
>     I thought Scalar was only used internally by the assembler? That's why I
>     didn't consider this an interface change.
>
>     Martin
>
>     On 20 November 2014 14:22, Martin Sandve Alnæs <marti...@simula.no> wrote:
>
>         That's correct, I extended Scalar to work properly in parallel to fix
>         that bug.
>
>         I think I found the idea of "operator double" dubious because it will
>         now involve MPI communication. It's only used from inside the
>         assembler.
>
>         The function get_scalar_value is public mainly to keep the tests
>         working, as I discovered unit tests that didn't work before.
>
>         Martin
>
>         On 20 November 2014 14:18, Jan Blechta <blec...@karlin.mff.cuni.cz>
>         wrote:
>
>             Maybe because of this
>             https://bitbucket.org/fenics-project/dolfin/issue/388/
>             scalar-apply-is-wrong
>
>             Jan
>
>
>             On Thu, 20 Nov 2014 14:12:36 +0100
>             Anders Logg <l...@chalmers.se> wrote:
>
>             > When was this added to Scalar and when/why was conversion to
>             double
>             > removed?
>             >
>
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