Operator Declarations

     :- op(1200, xfx, [+:,-:,+?,-?]).
     :- op(760,  yfx, #<=>).
     :- op(750,  xfy, #=>).
     :- op(750,  yfx, #<=).
     :- op(740,  yfx, #\/).
     :- op(730,  yfx, #\).
     :- op(720,  yfx, #/\).
     :- op(710,   fy, #\).
     :- op(700,  xfx, [in,in_set]).
     :- op(700,  xfx, [#=,#\=,#<,#=<,#>,#>=]).
     :- op(550,  xfx, ..).
     :- op(500,   fy, \).
     :- op(490,  yfx, ?).
     :- op(400,  yfx, [/>,/<]).