On 25.08.2012 10:40, Chris Smith wrote:
We have that, but I think it uses the unconventional R to L rather
than L to R convention:
p=Permutation
p([[1,2],[0],[3]])*p([[2,3],[0],[1]]
... )
Permutation([0, 2, 3, 1])
_.cyclic_form
[[1, 2, 3], [0]]
http://en.wikipedia.org/wiki/Cycle_notation says that the answer of
the above should be (132) not (123) (which is what SymPy gives when
the order of multiplication is reversed).
Actually, that is very bad I think. If it doesn't follow standard
conventions and notations,
people will not use it.
I've got this fixed but there are lots of failures in other areas of
combinatorics so i might as well close this for now. I (as you)
consider this a show stopper.
Huh? At least in my courses, cycles where just a short-hand notation for
permutations, and where composed in precisely the way this code does. I
know there are arguments for composing on the right, but I don't think
this is universally done (or even by a majority). I don't know about
specialised fields, though (e.g. there is a famous crystallography book
composing on the right, but even in its field it is an exception, not
the rule).
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