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.
This will:
* remove the need for metaclasses,
* make it explicit that we are using compiled stuff
* easier to maintain (soon leaving you know :) )
> My next problem now is that one needs to set the geometric dimension
> at the time of construction for a C++ expression. How can I send this
> to my Expression sub class from Python?
For now you have to instantiate the parent Expression in your C++ code. This
could be done with:
code = """
class MyExpression : public Expression
MyExpression() : Expression(%d)
...
"""
f = Expression(code%mesh.geometry().dim(), V=V)
But this you have already found out...
Johan
> --
> Anders
>
> On Fri, Oct 16, 2009 at 01:29:57PM +0200, Anders Logg wrote:
> > I'm getting this error with a code that used to work:
> >
> > f = Expression(code, V=V)
> >
> > File
> >
> > "/home/logg/scratch/src/dolfin-dev/local/lib/python2.6/site-packages/dolf
> >in/expression.py", line 575, in __new__
> > [element.cell().geometric_dimension()])[0]
> > File
> >
> > "/home/logg/scratch/src/dolfin-dev/local/lib/python2.6/site-packages/dolf
> >in/compile_expressions.py", line 216, in compile_expressions
> > classname, code = expression_to_dolfin_expression(cpparg,
> > defaults, dim)
> > File
> >
> > "/home/logg/scratch/src/dolfin-dev/local/lib/python2.6/site-packages/dolf
> >in/compile_expressions.py", line 65, in expression_to_dolfin_expression
> > fragments = expression_to_code_fragments(expr, defaults,
> > ["v","x"])
> > File
> >
> > "/home/logg/scratch/src/dolfin-dev/local/lib/python2.6/site-packages/dolf
> >in/compile_extension_module.py", line 66, in expression_to_code_fragments
> > raise TypeError, "The c++ keyword '%s' was detected in C++
> > expression."%sym
> > TypeError: The c++ keyword 'class' was detected in C++ expression.
> >
> >
> >
> >
> > _______________________________________________
> > DOLFIN-dev mailing list
> > DOLFIN-dev@fenics.org
> > http://www.fenics.org/mailman/listinfo/dolfin-dev
>
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