On Friday 16 October 2009 14:44:31 Anders Logg wrote:
> On Fri, Oct 16, 2009 at 02:39:36PM +0200, Johan Hake wrote:
> > On Friday 16 October 2009 13:51:18 Anders Logg wrote:
> > > My fault. The problem here was that I forgot to change from Function
> > > to Expression in the code string. But perhaps the check needs to be
> > > improved? The error message does not help.
> >
> > I think we need to extend the syntax if we want to have better messages.
> > Now we first search for the string:
> >
> > "class () public:Expression"
> >
> > If this is found we assume that the user wants to create a complex
> > Expression.
> >
> > When this is not found we assume that the user want to create an
> > Expression based on the simple syntax. We then check if any C++ keywords
> > are used in that string, and it was this check that kicked in for you.
> >
> > If we want to keep the syntax we might change the error to:
> >
> > TypeError: You are trying to compile a simple Expression and the C++
> > keyword 'class' was detected in the passed string.
> >
> > We might also change the syntax all the way and make things easier for
> > us. (More drastic change though...)
> >
> > * class Expression is only used to subclass Expression in pure Python.
> > * function CompileExpression is used to compile:
> > 1) simple expressions
> > 2) complex expressions
> > Where we use kwargs do differentiate between the two.
> > * As before CompileExpression takes an ufl.FiniteElement or a
> > FunctionSpace to instantiate the compiled class.
> > * CompileExpressions can do what Expressions do now, creating several
> > classes
> > * Remove the possibility to create compiled classes, only
> > instantiated ones.
>
> What does this last point mean? I have never used this (I think).
Exactly! Another good point for removing it ;)
Now you can create a compiled expression class by:
class MyExpression(Expression):
cpparg = ["sin(x[0])","code(x[1])"]
not an instantiated one.
> > This will:
> > * remove the need for metaclasses,
> > * make it explicit that we are using compiled stuff
> > * easier to maintain (soon leaving you know :) )
>
> I think this would be good. I for one don't understand the metaclass
> stuff well enough to maintain it.
>
> If we go this way, then I suggest naming it "CompiledExpression".
Agree with the naming.
However not sure when I would get the time to fix this if we go for the
suggested change...
Johan
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