Aliases

[Hasan Aljudy]

Bill Baxter wrote:
> rm wrote:
>> Reiner Pope wrote:
>>
>>> What's the purpose of the restriction of alias in the specs -- 'Aliases
>>> cannot be used for expressions'; it prevents some useful things like 
>>> this:
>>>
>>>  int[2] nodes;
>>>  alias nodes[0] left;
>>>  alias nodes[1] right;
>>>
>>> which currently has to be written in a much more hackish way:
>>>
>>>  union {
>>>    int[2] nodes;
>>>    struct {
>>>       int left;
>>>       int right;
>>>    }
>>>  }
>>>
>>> This is less reliable because if you decide to change the datatype of
>>> nodes, you could easily stuff up:
>>
>>
>> you could do this:
>>
>>   template KT(T)
>>   {
>>     union KT
>>     {
>>       T[2] nodes;
>>       struct
>>       {
>>         T left;
>>         T right;
>>       }
>>     }
>>   }
>>
>>   alias KT!(int) K;
>>
>> roel
> 
> Or in this case he's not even after a template, so just
>   union {
>     alias int NodeID;
>     NoteID[2] nodes;
>     struct {
>        NodeID left;
>        NodeID right;
>     }
>   }
> 
> But, I see your point, Reiner.  'alias foo[1] bar' expresses the intent 
> of the programmer more clearly here than union, and doesn't have the 
> typesafety issues.
> 
> --bb

I think this is a typesafe solution:
typeof(node[1]) left;
typeof(node[2]) right;