Re: The simple Image issue

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 31 Aug 2011 17:08:51 +0100, Simon Wright wrote:

> Hyman Rosen <hyrosen@mail.com> writes:
> 
>> On 8/31/2011 2:16 AM, Georg Bauhaus wrote:
>>> In which way would you change T'Value for symmetry?
>>
>> You wouldn't, because the symmetry is false. When you
>> already have an object, being forced to name its type
>> is silly and redundant. When you have a string and want
>> it converted to an object, of course you need to say
>> what type it's becoming.
> 
> I would have thought overload resolution would solve a lot of problems?
> 
>    X : Integer := "123"'Value;
>    Y : Float := "1.0e-9"'Value;

Yes, in my string editing library, it is just overloaded functions:

   X : Integer := Value ("123");
   Y : Float := Value ("1.0e-9");

No problem to resolve. The real problem is that the thing is generic. A
built-in function does not need boring instantiations.

P.S. There exist subtle issues with subtypes, e.g. 

   X : Positive := Value ("-123");

The question is whether the constraint has to be known within the operation
or not. In most cases the operation can operate on the parent checking the
constraint upon setting the target:

   Positive's Value = Positive o Integer's Value

But for things like enumeration extensions (i.e. subtypes weakening
constraints rather than strengthening them), this would become a problem.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de