Hi Martin!
On Sep 4, 12:33 pm, Martin Albrecht <m...@informatik.uni-bremen.de>
wrote:
[..]
> Think this would be rather un-pythonic: converting an object into a string
> instead of using it directly.
>
> > But what about block orderings? If one allows a matrix ordering to be
> > defined by a matrix, then I guess the blocks should be listed:
> > sage: P.<a,b,c,d,e> = PolynomialRing(QQ,5,order=[M,'degrevlex'])
>
> Have you seen this?
>
> sage: TermOrder('deglex',3) + TermOrder('degrevlex',2)
> deglex(3),degrevlex(2) term order
Meanwhile I've also seen the code of TermOrder.__add__. It is rather
un-pythonic, as it entirely relies on working with strings.
Namely:
...
name = []
for block_order in self.blocks + other.blocks:
nom = block_order.singular_str()
name.append("%s(%d)"%(inv_singular_name_mapping.get
(nom,nom), len(block_order)))
name = ",".join(name)
return TermOrder(name, len(self)+len(other))
In other words, for each block, the defining string for the order in
Singular is translated into a defining string for the order in Sage,
by a dictionary lookup (inv_singular_name_mapping.get(nom,nom), then
everything is concatenated and given as the input to
TermOrder.__init__.
Problem: singular_str() for a matrix order will be M(1,3,1,0,...),
where the number of integers between the brackets depends on the
lengths. This can't be dealt with by a simple dictionary lookup.
So, a proper support of Matrix orders will be more work, and wrapping
things in libsingular will not suffice.
Best regards,
Simon
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