private int opPrecedence(Operator opr, int sid) {
    if     (opr==null)                            { return Integer.MIN_VALUE;                                    } // not an operator
    else if(opr.unary==NO_SIDE || opr.unary!=sid) { return (sid==LEFT_SIDE ? opr.precedenceL : opr.precedenceR); } // operator is binary or is unary and bound to the operand on the other side
    else                                          { return Integer.MAX_VALUE;                                    } // operator is unary and associates with the operand on this side
    }