On Sat, Aug 25, 2012 at 4:12 PM, Tom Bachmann <[email protected]> wrote: > > > 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).
It's as it was, using L to R but I added a reverse option so one can go R to L if desired. -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
