string ring_of_q_difference_operators This command has not been maintained since 1996. So, there may be troubles if it is used with new features of kan/sm1. This command is used to define a ring of q-difference operators with the macros define_qring, weight_vector and elimination_order. Note that you should use this macro with define_qring instead of define_ring. The user cannot use the variable names h, e, q and E. cf. show_ring, system_variable --- CurrentRing print_switch_status, switch_function Example: [(x,y,z) ring_of_q_difference_operators (Qx,Qy) elimination_order 0] define_qring Qx,Qy, and Qz are corresponding q-difference operators to the space variables x, y and z ( Qx x = (q) x Q).