:- op(500,xf,nooot).
:- op(500,yf,psyche).

nooot(X):- \+X.

psyche(X):- \+X.

person(tristan).
person(beth).
person(dv).
person(evan).

%---
:- op(100,xfy,or).
:- op(150,fx,either).

%either A or B:-
%	(A,\+B);(\+A,B).

%either(or(A,B)).

either P or Q:-
	(P->A=1;A=0),
	(Q->B=1;B=0),
	1 is A+B.