On Wed, Mar 12, 2014 at 06:41:07AM -0700, Eric Gourgoulhon wrote:
> In order to treat tensor fields on a parallelizable domain N of some
> smooth manifold as elements of a free module (cf. #15916 and this post),
> one has first to introduce the commutative ring C^oo(N) of smooth
> functions N --> R, as a new class, ScalarFieldRing say. Browsing through
> Sage reference manual, a natural guess would be to make it a subclass of
> CommutativeRing:
You don't necessarily need too. You could also just inherit from
Parent; the important thing is to set the category to
CommutativeRings().
CommutativeRing is a bit of a legacy stuff: it's still there because
some features have not yet been moved to categories, and also because
some parents where pure arithmetic speed on elements is vital
(e.g. small finite fields), need it to by Cython.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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