#11847: unexpexted behavior of degree() with matrix ordering
-----------------------------------+----------------------------------------
Reporter: john_perry | Owner: malb
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.7.2
Component: commutative algebra | Keywords: degree, polynomial,
singular
Work_issues: | Upstream: Not yet reported
upstream; Will do shortly.
Reviewer: | Author: john_perry
Merged: | Dependencies: sage 4.7.2
-----------------------------------+----------------------------------------
Comment(by john_perry):
Replying to [comment:3 klee]:
> I don't see natural use cases for total_degree_ungraded() when one use
non-default grading with a polynomial ring.
I discovered the problem when the grading changed while working with a
matrix term ordering. It appears whenever one uses a matrix ordering, and
`total_degree()` is not an uncommon tool.
> The name is also confusing.
One goal was that the user find it easily when performing tab-completion,
'''and''' would see that there are two different notions of ''total
degree'' in play, prompting her or him to read the docstring. With that in
mind, I aimed for a name that would be clear. It slipped from my mind that
the ring is never ungraded, so I agree that this is a very, very bad name.
I had toyed with `total_degree_exponents()` as well. I could see
`exponent_total_degree()`, but thought that harder for a user to find
using tab-completion.
> On the other hand, exponent(x) method, which Maarten suggested, would be
useful and essential.
Actually, I suggested that name. :-) Maarten didn't suggest a particular
name, but that there should be a different set of functions for ungraded
degree. I originally set out to do as you suggest, but as I thought about
it, several considerations presented themselves:
1. The method `degree(x)` already exists, and does the same.
1. It seems unwise to deprecate `degree(x)`, which is probably used in a
lot of code by a lot of people. (''I've'' used it a lot, anyway.)
1. The patch could leave `degree(x)` alone, and introduce `exponent(x)`
(or whatever name) which merely replicates the behavior. I'm not opposed
to that, but I wanted someone else's input first. I recall there was
discussion of a similar duplication of methods in linear algebra some
years ago (see e.g. `eigenvectors_right` and `right_eigenvectors`).
1. I'd ''prefer'' to change `degree()` to behave as if the ring had the
standard grading, and define `degree_in_grading()` (or something similar)
to behave the way Singular defines it. Again, that could have an impact on
how people have already been using `degree()` in code.
These thoughts prompted me to start with an incremental patch initially,
which could be modified according to comments.
> Moreover you can make exponent() to return the sum of all exponents of
the variables in the monomial, making total_degree_ungraded() redundant.
'''That''' would be confusing to me; I've never seen ''total degree''
referred to as ''exponent''. I would prefer a different name if we take
that route, such as `exponent_total_degree()` or
`total_degree_exponents()`. Or even something clearer.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11847#comment:4>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
