operator[-100] (+ a) a.affirm;
  operator[-100] (- a) a.negate;
  operator[-100] (! a) a.not;
  operator[-100] (# a) a.hashCode;
  operator[-100] (@ a) a.identity;

  operator[80] (a * b) a.times(b);
  operator[80] (a / b) a.divide(b);
  operator[80] (a % b) a.modulo(b);
  operator[80] (a & b) a.meet(b);

  operator[70] (a + b) a.plus(b);
  operator[70] (a - b) a.minus(b);
  operator[70] (a | b) a.join(b);
  
  operator[60] (a < b) a.lessThan(b);
  operator[60] (a > b) a.moreThan(b);
  operator[60] (a <= b) a.lessEqual(b);
  operator[60] (a >= b) a.moreEqual(b);
 
  operator[50] (a == b) a.identical(b);
  operator[50] (a != b) a.notIdentical(b);
  operator[50] (a = b) a.equal(b);
  operator[50] (a /= b) a.notEqual(b);
  
  operator[40] (a & b) a.and(b);
  
  operator[30] (a | b) a.or(b);
  
  operator[20] (a -> b) a.implies(b); 
  
  operator[-10] (a := b) a.assign(b);