#13646: Bug in p.add_constraint (when input is True/False)
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Reporter: ncohen | Owner: ncohen
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.5
Component: linear programming | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Nathann Cohen, Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Comment (by dimpase):
Replying to [comment:21 ncohen]:
> > I found a lot of places in the graphs stuff where `Sum(...) +
Sum(...)` occurs. As soon as one of the sums returns ``None`` this will
raise a `TypeError`.
>
> And if it never did, it may be because there is mathematical reason for
that, or did you make sure of the opposite ?
One surely can code in a very dangerous style, but this does not mean that
it should be forced upon they many Sage users.
E.g. #12091 (largely a duplicate of the current ticket) is a very good
example (actually, #12091 seems to be fixed by the Volker's patch---at
least the 1st example in the ticket description is fixed!) of pitfalls the
current LP code is creating.
For one, I would kill for Sum() returning what it should, and not None.
It's sad it might break some private code, but it's a fact of life. Sage
cannot always maintain the backward compatibility, after all. E.g. a move
to Python 3 will break stuff for a lot of people. Please show us a typical
fragment broken by Volker's patch, and we will see the best workaround.
(Well, it could be that all it needs is a private definition of Sum(),
can't tell without looking.)
> > We will remove the hardcoded RDF in #13650, so its just a matter of
time until its gone. Its not an option to hardcode RDF in Sum in the long
run.
>
> It has been an option to not have a base ring at all for a very long
while now.
Sure, but it was a bad design decision not to have one.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13646#comment:23>
Sage <http://www.sagemath.org>
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