Thanks!
On May 23, 10:05 am, "Craig Citro" <[EMAIL PROTECTED]> wrote: > Hi Uptal, > > Yep, you're exactly right about what's causing this issue -- each time > you call SL2Z(), it creates a new object. However, there's no need for > this -- after all, SL2Z is a real mathematical object, so it should be > a distinct object in Sage, just like ZZ or QQ. So I've made this > change, and posted a patch at: > > http://trac.sagemath.org/sage_trac/ticket/3275 > > It'll be in the next version of Sage (3.0.2). Note that this means > you'll want to use it slightly differently -- so your example would > become: > > sage: S = SL2Z([0,-1,1,0]) > sage: T = SL2Z([1,1,0,1]) > sage: S*T > [ 0 -1] > [ 1 1] > > Or better yet: > > sage: S = SL2Z.0 ; S > [ 0 -1] > [ 1 0] > > Definitely let us know if you run into any more trouble! > > -cc > > On Thu, May 22, 2008 at 2:14 PM, Utpal Sarkar <[EMAIL PROTECTED]> wrote: > > > Hi, > > > There are problems doing arithmetic in SL_2(Z): > > S,T = SL2Z().gens() > > S*T; # no problem > > S^2*T^3; # no problem > > S^-2*T^-3; # no problem > > but when I multiply two elements with different exponent: > > S^-2*T^3; > > S^2*T^-3; > > T^2*T^-3; > > I get a > > <type 'exceptions.TypeError'>: Cannot convert > > sage.matrix.matrix_integer_2x2.Matrix_integer_2x2 to > > sage.matrix.matrix_integer_dense.Matrix_integer_dense > > However, T.parent() and (T^-1).parent() return the same thing (both > > equal string values "Modular Group SL(2,Z)" and equal when directly > > compared with == and even with 'is'). > > When I do > > sage: S = SL2Z()([0,-1,1,0]) > > sage: T = SL2Z()([1,1,0,1]) > > sage: S*T > > I even get a runtime error: > > <type 'exceptions.RuntimeError'>: There is a bug in the coercion code > > in SAGE. > > In this case in fact the parents are not equal: they are when compared > > with ==, but not with 'is'. > > (That's fine, that is more something of the implementation) > > Finally, if I do > > sage: G = SL2Z() > > sage: S = G([0,-1,1,0]) > > sage: T = G([1,1,0,1]) > > then I can work correctly with S and T. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com 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 -~----------~----~----~----~------~----~------~--~---
