On Fri, Nov 27, 2009 at 11:59:52PM -0800, Johan Hake wrote: > Hello! > > I have not pushed anything, but Expressions should be up to shape now, and I > am working on simplifying the logic in other places of expression.py > > I do not like the implementation of the dim method. It is used to read a user > defined value dimension and then discarded. I suggest that we add a > value_shape attribute to the dolfin.Expression class. If not set by the user > it is by default (), i.e., a scalar Expression. > > class MyExpression(Expression): > value_shape = (2,) > def eval(self, values, x): > values[0] = 1 > values[1] = 1 > > The dim name is also only making sense for Vector Expressions, where I think a > value_shape attribute makes sense for all occasions. A value_shape for scalar > Expression will still be the default.
I think a dim method makes more sense than adding a variable since it is consistent with eval: Then all data a subclassed Expression needs to give is defined by a member function. If we need value_shape and value_dimension (which is good to have), can't we just store those values as _value_shape, _value_dimension after we have figured out the shape and provide member functions that return those values? Also note the clever/simplified interface for dim() allowing (1) not to overload it for scalars and (2) to return the just the vector dimension for vectors: n instead of (n,)). -- Anders > After creation and instantiation we then have an object that have both a shape > method (from ufl.Function) and a value_shape attribute from the subclassing > definition. > > What you think. > > Johan > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : [email protected] > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp
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