private int mapOp(boolean invert, int op) {
		switch (op) {
		case Expression.EQ:
			return Expression.GE;
		case Expression.GE:
			if (!invert) {
				return Expression.GE;
			} 
			return Expression.LE;
		case Expression.LE:
			if (!invert) {
				return Expression.LE;
			}
			return Expression.GE;
		case Expression.LT:
			if (!invert) {
				return Expression.LT;
			}
			return Expression.GT;
		}
		return op;
	}