On 4/12/14, 5:59 AM, Jonathan M Davis wrote:
On Friday, April 11, 2014 19:52:58 Andrei Alexandrescu wrote:
On 4/11/14, 6:59 PM, Jonathan M Davis wrote:
On Friday, April 11, 2014 17:01:15 Andrei Alexandrescu wrote:
On 4/11/14, 12:31 PM, Jonathan M Davis wrote:
On Friday, April 11, 2014 08:22:01 Steven Schveighoffer wrote:
final enum name { ... }
This only makes sense to me if it's then illegal to declare any
variables
of that enum type, because if you're looking to use an enum to give a
list of possible values rather than enumerating the exact list of
values,
why would you be marking _any_ variable as being of that enum type?
I don't understand that contention. "final" clarifies that the set of
values in the enumeration is closed.
I take issue with the idea that it makes sense to have any variables of an
enum type that isn't one of the values enumerated in the enum.
I explained the possible situations in the original post of this thread.
E.g. one may be unable to enumerate all user IDs, but may be compelled
to enumerate a few remarkable ones and ascribe user IDs a separate type.
-- Andrei
And what would the purpose by of giving them their own type?
Less error proneness.
If the enum
doesn't enumerate all of the values, then you're clearly going to be using
other values with it, meaning that any restrictions on setting a variable to
those other values is going to be a problem (as is currently the case with
enums - assignment and initialization are protected against non-enumerated
values). You'd just end up with a enum type which is effectively an alias for
the enum's base type except that assigning it non-enumerated values requires
casting, and you can overload a function on the enumerated values vs the non-
enumerated ones (or at least, non-enumerated ones which aren't cast to the
enum type) by overloading a function on the enum type and its base type -
which would be highly bug-prone IMHO.
Sorry, your speculations are mistaken. The pattern works well and we've
been using it repeatedly and with good results since C++ introduced
"enum class".
Andrei
