:- op(1150,  fx, (function)).
:- op(1150, xfx, (:=)).
:- op(  50,  fx, (~)).
:- op( 910,  fx, (^^)).
:- op(  25,  fy, (^)).
:- op(1100, xfy, ('|')).
:- op(1050, xfy, (?)).
