On Sun, Aug 26, 2012 at 7:50 PM, David Joyner <wdjoy...@gmail.com> wrote: > On Sun, Aug 26, 2012 at 9:39 AM, Chris Smith <smi...@gmail.com> wrote: >> Here's another idea: create a DisjointCycle object for which >> multiplication is R to L. In use it would look like this: >> >>>>> C = DisjointCycle >>>>> C(1, 2)*C(2, 3) >> (1, 3, 2) >>>>> Permutation(_).array_form(0) >> [0, 3, 1, 2] >> > > How would these be used to construct permutation group? > If you used elements of this class then the elements of a > perm group would not be Perms but DisjointCycles? >
in order to preserve the R to L multiplication, yes, they would have to stay DC. But to convert to Permutation I would allow Permutation to accept DC as shown above. DisjointCycle is a defaultdict that gives a value equal to the key. Multiplication switches around the entries. If an element hasn't been addressed it returns itself. So in c, the first element, 3, is at position 1 whereas in >>> C(0, 1)*C(1,2) (0, 2, 1) the first 0 is at position 0 and in >>> C(3, 4)*C(4, 5) (3, 5, 4) the first position is at 3. Conversion to array form will fill in the missing values as in >>> [_[i] for i in range(6)] [0, 1, 2, 3, 5, 4] /c -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
