On Fri, Sep 05, 2014 at 07:58:30AM -0700, Dima Pasechnik wrote: > I just had a quick look at it, and the following looks downright scary:
> + For backward compatibility, if a permutation group element > + acts on the integers `\{1,\ldots,n\}` or a subset thereof, > + the columns are considered as being numbered from `1`:: > + > + sage: G = PermutationGroup(['(1,2,3)(4,5)', > '(1,2,3,4,5)']) > + sage: sigma, tau = G.gens() > + sage: sigma > + (1,2,3)(4,5) > + sage: M = copy(N) > + sage: M.permute_columns(sigma) > + sage: M > + [1 0 1 0 0] > + [2 2 0 0 0] > + [0 3 0 0 3] > + [0 0 0 4 4] > + [0 0 0 5 0] > note that there is an unpleasant ambiguity here: > namely, if, say in this example you take > G = PermutationGroup(['(1,2,3)']) > how one could tell whether it is meant to permute stuff in [0..2], or > in [1..3] ? > Do you mean that one must write G = PermutationGroup(['(0),(1,2,3)']) > for the latter? I agree it's not great. But do you have a better proposal? The current situation is a painful source of confusion, and is actually already ambiguous if one is not reading the specifications carefully: in your above example, the unwary user may well expect that he will permute stuff in [1..3]. The ticket only adds a new feature allowing for the natural 0-based permutations. Otherwise it does not change the current behavior. Cheers, Nicolas -- Nicolas M. ThiƩry "Isil" <nthi...@users.sf.net> http://Nicolas.Thiery.name/ -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.