Re: What's wrong with C++?

[Hyman Rosen <hyrosen@mail.com>]

On 2/17/2011 3:51 PM, Ludovic Brenta wrote:
> Hyman Rosen<hyrosen@mail.com>  writes:
>> C and C++ enumerations don't have arithmetic.
>> They do convert automatically to integers, but
>> they don't automatically convert back.
>
> Actually they do in the example you provided:
>
>      struct DamageType {
>          enum E { Fire = 1, Acid = 2, Lightning = 4, Poison = 8 };
>      };
>
>      DamageType::E what_my_dragon_can_do =
>          DamageType::E( DamageType::Acid | DamageType::Poison );
>
> In this example, the two enumeration values are automatically promoted
> to integer (which has arithmetic) ORed, then the result is automatically
> converted back to the type DamageType::E.

How is that automatic? It is explicitly converted back through
     DamageType::E( expression )

> Except that the value of what_my_dragon_can_do is not one of the
 > values defined in the type.

Once again, this is a design decision made by those who brought
enumerations into C. The value an enumeration may take is not
restricted to being one of the enumerators because the language
wants to support using enumeration literals as bitmasks. You may
not like it, but this use is correct C++.