Re: Refactor "mutually exclusive options" error reporting code in parse_subscription_options

At Fri, 11 Jun 2021 16:29:10 -0400, Robert Haas <robertmhaas(at)gmail(dot)com> wrote in
> On Tue, May 25, 2021 at 9:38 AM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> > This should be okay, right? Well, almost. The problem here is if you
> > want to have a variable where you set more than one option, you have to
> > use bit-and of the enum values ... and the resulting value is no longer
> > part of the enum. A compiler would be understandably upset if you try
> > to pass that value in a variable of the enum datatype.
>
> Yes. I dislike this style for precisely this reason.
>
> I may, however, be in the minority.

I personaly don't hate that so much, but generally an "enumeration"
type is considered to be non-numbers. That is, no arithmetics are
defined between two enum values. I think that C being able to perform
arithmetics on enums is just for implement reasons. I think that
arithmetics (logical operations are not arithmetics?) between boolean
values are for the same reasons. Actually Java refuses arithmetics on
enum values.

> hoge.java:27: error: bad operand types for binary operator '+'
> int x = theenum.x + theenum.z;
> ^
> first type: theenum
> second type: theenum

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center