:: HIDDEN semantic presentation

definition
mode set -> set ;
end;

definition
let x, y be set ;
pred x = y;
reflexivity
errorfrm
;
symmetry
errorfrm
;
end;

notation
let x, y be set ;
antonym x <> y for x = y;
end;

definition
let x, X be set ;
pred x in X;
asymmetry
errorfrm
;
end;