[sage-support] bug report with Rubik's cube functions
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 ! 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+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.
Re: [sage-support] bug report with Rubik's cube functions
On Thu, Mar 19, 2015 at 8:07 AM, Pierre pierre.guil...@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+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.
Re: [sage-support] bug report with Rubik's cube functions
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... 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 javascript: 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 javascript:. To post to this group, send email to sage-s...@googlegroups.com javascript:. 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.
Re: [sage-support] bug report with Rubik's cube functions
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.
