#20028: sorting of number field elements
-------------------------------------+-------------------------------------
Reporter: cremona | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.1
Component: number fields | Resolution:
Keywords: sort number field | Merged in:
elements | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: u/cremona/20028 | a8a0714ceb09eef1c5a9e1607b2dce5183d8763d
Dependencies: | Stopgaps:
-------------------------------------+-------------------------------------
Comment (by cremona):
Replying to [comment:18 gjorgenson]:
> Hi!
Thanks a lot for responding.
>
> I think the failure in projective_morphism.py comes from
projective_homset.py, where a set is now unexpectedly returned instead of
a list in the points function for fields. The try block that was added in
projective_homset.py prevents {{{sorted(points)}}} from executing in line
138 and {{{sorted}}} changes the type of points from a set to a list.
Changing {{{return points}}} to {{{return list(points)}}} in line 141
seems to address the problem.
OK, we'll do that. (It is odd to me that sorted(X) has the side effect of
changing a set to a list, but now that we know that we just make it into a
list regardless of whether we are able to sort it.)
I'll update the branch on this ticket accordingly.
>
> For the code in projective_morphism.py (lines 3003-3011) in the first
line a list is declared but is never used (I think it is an artifact from
a previous implementation attempt that wasn't caught). As far as I can
tell, the rest of the code is working properly. Is there a problem with
its functionality that I've missed?
Sure, rem_indices is not used. But also: the line P=self(P) is executed
man ytimes (once for each j) and in the next line should it not be if
p++points[j]? Otherwise j is not used. I am also worried about the
effect of popping points[i] while in the i-loop, but perhaps that's OK
given that the i loop goes backwards. A comment to explain what this
block of code is doing would help, since I suspect that someone might come
up with a slicker solution. (If we only wanted to remove duplicates and
did not care about the order then something like points=list(set(points))
would work.)
It's a nuisance that any fix to this will conflict with our sorting
changes, but we'll have to live with that.
--
Ticket URL: <http://trac.sagemath.org/ticket/20028#comment:19>
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 unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
