:- op(1200, xfx, --->).
:- op(1200, xfx, ===>).
:- op( 30, fy, ~).
:- op(500, xfy, &).
:- op(500, xfy, #).
:- op(510, xfy, =>).
:- op(510, xfy, <=>).
:- op(400, yfx, *).