#14251: Circulant digraphs
---------------------------------+------------------------------------------
Reporter: ncohen | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.9
Component: graph theory | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers: David Coudert
Authors: Nathann Cohen | Merged in:
Dependencies: | Stopgaps:
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Comment (by ncohen):
Yo !
> * I have read somewhere that imports should now be at module level, but
I'm not sure...
Cython imports should be, but that's all. Anyway you cannot have all
imports at module level, it wouldn't work. You need to use graph
generators in digraph.py, and you need to use digraphs
indigraph_generators too.
> * You should test that n>=0
Why not...
> * You should check that integers is an iterable (list, set, dict?) with
valid numbers (can we have negative numbers? what if a number is larger
than n? what to do with 0?)
If it is not iterable the "for j in integers" would fail with a clear
message :
{{{
sage: digraphs.Circulant(4,5)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-2-50bde61731c6> in <module>()
----> 1 digraphs.Circulant(Integer(4),Integer(5))
/home/ncohen/.Sage/local/lib/python2.7/site-
packages/sage/graphs/digraph_generators.pyc in Circulant(self, n,
integers)
407
408 for v in range(n):
--> 409 G.add_edges([(v,(v+j)%n) for j in integers])
410
411 return G
TypeError: 'sage.rings.integer.Integer' object is not iterable
sage:
}}}
I will add some checks.. And I really hate when a 3-lines code takes 10
lines to check bad input... Users should learn to deal with them too.
Nathann
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14251#comment:3>
Sage <http://www.sagemath.org>
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