Interesting rant about Scala's issues

[Regan Heath]

On Mon, 07 Apr 2014 16:15:41 +0100, Paulo Pinto <pjmlp at progtools.org>  
wrote:

> Am 07.04.2014 12:07, schrieb Regan Heath:
>> On Mon, 07 Apr 2014 00:17:45 +0100, Andrei Alexandrescu
>> <SeeWebsiteForEmail at erdani.org> wrote:
>>
>>> On 4/6/14, 10:52 AM, Walter Bright wrote:
>>>> On 4/6/2014 3:31 AM, Leandro Lucarella wrote:
>>>>> What I mean is the current semantics of enum are as they are for
>>>>> historical reasons, not because they make (more) sense (than other
>>>>> possibilities). You showed a lot of examples that makes sense only
>>>>> because you are used to the current semantics, not because they are  
>>>>> the
>>>>> only option or the option that makes the most sense.
>>>>
>>>> I use enums a lot in D. I find they work very satisfactorily. The way
>>>> they work was deliberately designed, not a historical accident.
>>>
>>> Sorry, I think they ought to have been better. -- Andrei
>>
>> Got a DIP/spec/design to share?
>>
>> R
>>
>
> How they work in languages like Ada.

Ok, brief look at those shows me enums can be converted to a "Pos" index  
but otherwise you cannot associate a numberic value with them, right?

So if we had that in D, Walters examples would look like..

1)

   enum Index { A, B, C }
   T[Index.C.pos + 1] array; // perhaps?
   ...
   array[Index.B.pos] = t;   // yes?

2)

   array[Index.A.pos + 1] = t; // yes?

3)

   enum Mask { A=1,B=4 } // not possible?

   Mask m = A | B;   // Error: incompatible operator | for enum


Have I got that right?

For a proposal like this to even be considered I would imagine it would  
have to be backward compatible with existing uses, so you would have to be  
proposing a new keyword or syntax on "enum" to trigger typesafe enums,  
perhaps "typesafe" is a good keyword, e.g.

typesafe enum Index { A, B, C } // requires use of .pos to convert to int  
0, 1, or 2.
enum Index { A, B, C }          // existing pragmatic behaviour

R

-- 
Using Opera's revolutionary email client: http://www.opera.com/mail/