On Jun 30, 7:00 pm, "David Joyner" <[EMAIL PROTECTED]> wrote:
> In that case, this might do it
>
> sage: PermutationOptions(display='list')
> sage: L1 = [5,3,8,6]
> sage: L2 = copy(L1)
> sage: L1.sort()
> sage: L = [L2.index(x)+1 for x in L1]
> sage: p = Permutation(L); p; p.to_cycles()
> [2, 1, 4, 3]
> [(1, 2), (3, 4)]
> sage: p.signature()
> 1
> sage: p.to_permutation_group_element().sign()
> 1
>
Okay, thanks, that's a bit cleaner than what I had worked out.
> On Mon, Jun 30, 2008 at 9:12 PM, John H Palmieri <[EMAIL PROTECTED]> wrote:
>
>
>
> > On Jun 30, 5:16 pm, "David Joyner" <[EMAIL PROTECTED]> wrote:
> >> Do you mean the tuple is represented in the disjoint cycle notation and
> >> is a cyclic permutation? In that case, you can use:
>
> >> sage: PermutationGroupElement('(3,6,4)').sign()
> >> 1
> >> sage: PermutationGroupElement('(5,3,6,4)').sign()
> >> -1
>
> > No, by "one-line permutation notation", I mean that (3,6,4) means the
> > permutation where 3 -> 3, 4 -> 6, and 6 -> 4, while (5,3,8,6) is the
> > permutation of (3,5,8,6) in which 3 and 5 have been interchanged, as
> > have 6 and 8.
>
> >> On Mon, Jun 30, 2008 at 7:17 PM, John H Palmieri <[EMAIL PROTECTED]> wrote:
>
> >> > Suppose I have a tuple x of distinct non-negative integers. Is there
> >> > a quick way to find the sign of this, as a permutation of Set(x)? (I
> >> > want to view x as the one-line permutation notation form, so (3,6,4)
> >> > will have sign -1, while (5,3,8,6) will have sign 1.)
>
> >> > The things I can find in combinat/... don't quite seem to do what I
> >> > want. I can build something myself, but if there is a quick solution,
> >> > I would prefer that.
--~--~---------~--~----~------------~-------~--~----~
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/sage-support
URLs: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
