#12630: Add representations of quivers and quiver algebras to sage
-------------------------------------+-------------------------------------
Reporter: JStarx | Owner: AlexGhitza
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.2
Component: algebra | Resolution:
Keywords: algebra, quiver, | Merged in:
module, days49 | Reviewers: Simon King
Authors: Jim Stark, Simon | Work issues:
King, Mathieu Guay-Paquet, Aladin | Commit:
Virmaux | b2248e0da6dcd8b6c07ff91db00491ce673576e8
Report Upstream: N/A | Stopgaps:
Branch: |
public/combinat/quivers |
Dependencies: #12412, #12413, |
#14806, #15491, #15623, #15810 |
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Comment (by darij):
I've just pushed a number of minor doc improvements along with the
occasional sourcecode edit (mainly `base_ring.one()` instead of
`base_ring(1)`). This is a result of several hours of trying to find bugs,
unsuccessfully. But there is a code smell which I'm really not happy with,
despite it being mentioned in several comments in the code:
{{{
sage: Q = DiGraph({1:{2:['a'], 3:['b']}, 2:{4:['c']},
3:{4:['d']}}).path_semigroup()
sage: P = Q.P(QQ, 2)
sage: v = P.zero()
sage: v.set_element([1], 2)
sage: v._elems
{1: (), 2: (1), 3: (), 4: (0)}
sage: P.zero()._elems
{1: (), 2: (1), 3: (), 4: (0)}
}}}
So we can change the cached `P.zero()` by using an exposed set-element
method. Is there a way to prevent this from happening? I fear just
mentioning it in comments is not enough; someone *will* trip over this.
This is as close as I can get to giving this a review (I fear I have
neither time nor competence to do a systematic review of this). All in
all, I'm seeing good and well-documented code here; this certainly will be
a very nice update to Sage.
--
Ticket URL: <http://trac.sagemath.org/ticket/12630#comment:235>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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