On Monday 18 January 2010 10:33:46 Anders Logg wrote: > On Mon, Jan 18, 2010 at 10:23:54AM -0800, Johan Hake wrote: > > On Monday 18 January 2010 08:29:03 dbeacham wrote: > > > New question #97842 on DOLFIN: > > > https://answers.launchpad.net/dolfin/+question/97842 > > > > > > Is there a less hacked way to add extra parameter values to be used in > > > an Expression in python than: > > > > > > class MyExp(Expression): > > > def __new__(cls, *args, **kwargs): > > > obj = Expression.__new__(cls, **kwargs) > > > return obj > > > > > > def __init__(self, *args): > > > .... > > > .... > > > > It has been possible to pass user defined optional arguments to the > > __init__ method. But it looks like a regression has kicked in. > > > > I have fixed the regression in dolfin dev, and added a doc string > > example. > > > > You should now be able to do: > > > > class MyExp(Expression): > > def __init__(self, **kwargs): > > self._mesh = kwargs['mesh'] > > self._domain = kwargs['domain'] > > def eval(self, values, x): > > info(self._mesh, 1) > > info(self._domain, 1) > > > > mesh = UnitCube(1,1,1) > > domain = MeshFunction("uint", mesh, 0) > > e = MyExp(mesh=mesh, domain=domain) > > e(0,0,0) > > > > Do not use *args and do _not_ call the base class __init__. Yes, it is > > counter intuitive but it is a result of having the Expression class do > > both compiled Expressions and python derived Expressions. > > > > I prefer having two classes, CompiledExpression and Expression, so we > > could say goodbye to this kind of troubles ;) > > I'd prefer keeping "Expression" for the simplest option which is > visible in most demos: > > f = Expression("sin(x[0])") > > and find a suitable name for Expression with eval. > > Ideally, it should also be the same in C++.
So we could change Expression to let say UserExpression in C++ too. But I think this is double communication. Expression is a user defined expression and has to be sub-classed anyway. JIT compiling an expression in PyDOLFIN does quite a lot of magic behind the scenes and justifies a more explicit name like CompiledExpression or JITExpression. Clarity before beauty! > Candidates are > > UserExpression > ComplexExpression I still prefer CompileExpression and Expression, but wrt your suggestion I would go for the first one. Passing a mesh to an __init__ is not complex. Johan _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
