{ + }
               { - }
    value-expr { * } value-expr
               { / }

    An arithmetic expression combines value expressions and
    arithmetic operators. When you use an arithmetic expression in a
    value expression, the product using the CDO expression calculates
    the value associated with the expression and uses that value when
    executing the statement. Therefore, an arithmetic expression must
    be reducible to a value.

    The value expression, value-expr, is a symbol or a string of
    symbols used to calculate a value.