On Thu, Mar 19, 2015 at 10:43 AM, Pierre <pierre.guil...@gmail.com> wrote: > I agree. Surely in the code one has started with a right action (say) and > has then decided to sometimes convert it to a left action using inverses. > > However, some consistency would be good :-) After all, various pieces of > code seem to disagree on what U is... >
Yes, this is not documented well enough. Thanks very much for pointing this out! BTW, in case someone finds this sage-support thread via a google search, here is a page on switching between the left and right action conventions which might help: http://groupprops.subwiki.org/wiki/Switching_between_the_left_and_right_action_conventions > On Thursday, March 19, 2015 at 3:32:18 PM UTC+1, David Joyner wrote: >> >> On Thu, Mar 19, 2015 at 8:07 AM, Pierre <pierre....@gmail.com> wrote: >> > Hi, >> > >> > I have just realized this, and thought it would be helpful to know for >> > anyone playing with Sage's Rubik's cube abilitites. Here it is: >> > >> > While the following 3 commands: >> > >> > sage: CubeGroup().move("U") >> > >> > and >> > >> > sage: CubeGroup().plot3d_cube("U") >> > >> > and >> > >> > sage: RubiksCube().move("U").show3d() >> > >> > all take the convention that U means "move the face U clockwise", >> > unfortunately the command >> > >> > sage: RubiksCube().move("U") >> > >> > assumes that U means "move the face U counter-clockwise". >> > >> > So yes, doing foo= RubiksCube().move("U") and printing foo displays >> > something that is not consistent with what you get when calling >> > foo.show3d(). >> > >> > I thought it was something to do with 3d plotting being left-handed in >> > Sage >> > or whatever, but no, foo.show() also gives the "right" answer. And the >> > convention for what the permutation U is, taken by CubeGroup and given >> > in >> > Joyner's book, is just not the one appearing when you print foo. >> > >> > It seems that inverses are taken, since RubiksCube().move("R*U") >> > displays >> > something that corresponds to U^-1 * R^-1 (by which I mean U^-1 first, >> > then >> > R^-1). >> > >> > In a nutshell: the __str__ method in RubiksCube seems to be broken, >> > somehow. >> > >> > This is all quite confusing ! >> > >> >> I'm not sure, but I wonder if one describes a left action on a set and >> the other describes the right action. Left actions vs right actions >> are indeed confusing. However, some people insist on being lefties and >> others insist on being righties, so Sage is merely being agnostic in >> presenting both:-) >> >> That's my guess but I could easily be wrong. >> >> >> > best >> > Pierre >> > >> > >> > >> > >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups >> > "sage-support" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an >> > email to sage-support...@googlegroups.com. >> > To post to this group, send email to sage-s...@googlegroups.com. >> > Visit this group at http://groups.google.com/group/sage-support. >> > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-support+unsubscr...@googlegroups.com. > To post to this group, send email to sage-support@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-support. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
