a coset {W_PwW_Q} is represented by the list consisting of parabolic subgroups P and Q, and the representative of minimal length w

- minimalRepresentative(WeylGroupDoubleCoset) -- the minimal representative of a coset
- parabolic(WeylGroupDoubleCoset) -- the parabolic associated to a double coset
- WeylGroupDoubleCoset == WeylGroupDoubleCoset -- equality of double cosets

The object WeylGroupDoubleCoset is a type, with ancestor classes BasicList < Thing.