Dear all,

I would like to follow up on my differential forms class query (http://
groups.google.be/group/sage-devel/browse_thread/thread/
2feef1f0be557585/75173b6c6f52450d) with a question about Sage
programming/invoking style.

If R^n has coordinates x, y, ... (or whatever), then the algebra of
differential forms is generated by the differentials dx, dy, ...  (the
differentials of each of the coordinate functions).  So there's a one-
to-one correspondence between generators and coordinates on the
underlying space.  Is it allowable programming practice to implement
the DifferentialForms class so that the following construction becomes
possible:

sage:   F.<x, y, z>  = DifferentialForms()
sage:   F.gens()
>>>>      (dx, dy, dz)

but also
sage:  x in F.gens()
>>>>      False

That is, should the names between <> be exactly the generators
themselves, rather than something which can be made into a generator
in a non-canonical way?

I am not entirely comfortable with this approach, but in this way I
avoid having to check whether the names, number, ... of generators are
correct, since ParentWithBase.__init__ takes care of that.

All the best,
Joris

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