Hi all, Here are a few suggestions:
(1) permutations have a to_matrix() method; permuting the rows of M according to the permutation sigma can be done by M= M * sigma.to_matrix() and for the rows: M= sigma.to_matrix().transpose() * M Of course there is a debate about the behaviour of to_matrix() ; however i think the code for matrices should rely on to_matrix(), and then at least the conversation would be strictly one about the code for permutations. This answers a complain above. (2) if sigma is a permutation, i don't think sigma[i] should make sense at all. This requires the user to appreciate that sigma is implemented as a list, which i think is not a good idea. Of course some people (including me) want the permutation as a word; why not have a as_word() method, which could take a bunch of parameters for shifting (starting from 0 instead of 1 for example...) ? Also, permutations should always print in cycle notation, just like in GAP ! It's much easier to read, and drives the user away from the idea that the permutation "is" a list. [By the way, i also don't think sigma(i) should be implemented. The permutations in Sage act on the right, so i^sigma, just like in GAP, is more logical. This is not a very useful comment as changing the behaviour of standard ints is complicated (if possible at all?), and backward compatibility is needed.] (3) in fact i agree that permutations should not be implemented as lists, and should be thought of as acting on all integers from 0, as was suggested. Would the multiplication be as fast if they were stored as lists of cycles? I'm thinking that an implementation as a dictionnary, much like a sparse matrix, would be reasonable. (4) Here's a notation I use when I have a lot of permutation to input interactively: def C(*args) : # C for "cycle" -- 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.
