On Tue, Jan 12, 2010 at 03:58:32PM -0500, Jason Bandlow wrote: > > phi is constructed from f, which itself can't be pickled: > Thanks for your help on this!
My pleasure :-) > I now have a patch up at > > http://trac.sagemath.org/sage_trac/ticket/7914 > > in case you want to see if I understood you. :) Cooool! I'll look at this in detail soon. In the mean time, here are a couple thoughts. Sorry, it would have been best to raise them before your cleanup, but they came up while browsing through the patch ... - do we want leading_term or lterm (less explicit, but used in most systems)? You might want to raise that on sage-devel. - self._monomial_coefficients is specific to the CombinatorialFreeModule implementation. But you can use directly x[k] to get the coefficient of k in an element x of a module with basis. By the way, at some point, we should have an ModulesWithBasis(...).example(), with a very minimal implementation to catch this kind of things in tests. - trailing_term could possibly be implemented in terms of leading_term(..., -cmp) (well, -cmp is not valid python but you see the idea) - trailing_term should return a term Now, we hit the question of what a term is, and what a monomial is. We currently use MuPAD's convention that x^3 is a term, while 2*x^3 is a monomial. But other system use the reverse convention. It's kind of the last occasion we have to change that; it might actually be too late. Still, could you raise the issue on sage-devel? - a typical use case is: (support, coeff) = x.leading_blurb() It seems a waste to create a monomial as an element of the free module just to extract right after the support and coeff. Any idea on a good name for leading_blurb that would just return a pair? maybe x.leading_item, consistent with items/iteritems/... of dictionaries? Then, the other methods could be implemented in term of that low level function. - Suggestion: given how it is used, use an attribute self._upper set to True/False, rather than self.triangularity set to upper/lower. Alternative: handle the upper/lower logic once for all in the constructor by defining an attribute self._leading_term set to attrcall("leading_term", cmp) or attrcall("trailing_term", cmp). - move most of the code of _invert_on_basis into a public method self.preimage(x), and let _invert_on_basis(i) call self.preimage(codomain.term(i)) This will open the door for later generalization to non injective triangular morphism, and partial preimages. - rename the private _invert_on_basis into a public method preimage Thanks much! Nicolas -- Nicolas M. Thiéry "Isil" <nthi...@users.sf.net> http://Nicolas.Thiery.name/
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