Re: How to best make a custom range?

[Shark8 <onewingedshark@gmail.com>]

On Monday, November 4, 2019 at 10:56:15 AM UTC-7, Shark8 wrote:
> On Monday, November 4, 2019 at 10:26:22 AM UTC-7, Andrew Shvets wrote:
> > Lets say I have the following code:
> > 
> > subtype Test_Char is Character range ‘A’ .. ‘Z’;
> > 
> > But what if I wanted to include ‘&’, ‘@‘ and ‘?’ in this custom range of characters as well?  I thought of doing the following, but this obviously failed:
> > 
> > subtype Test_Char is Character range ‘@‘ | ‘&’ | ‘?’ | ‘A’ .. ‘Z’;
> > 
> > Or is this impossible unless I use a different approach?
> 
> 
> The approach I've been going with is splitting things apart into parts:
> 
>   Subtype Upper  is Character range 'A'..'Z';
>   Subtype Lower  is Character range 'a'..'z';
>   Subtype Symbol is Character
>     with Static_Predicate => '&' | '@' | '?';
> 
>   Subtype Test_Character is Character
>     with Static_Predicate => Upper | Lower | Symbol;
Ah, I forgot the SUBTYPE_NAME IN check, as well as the PREDICATE_FAILURE aspect.
Try:

   Subtype Upper  is Character range 'A'..'Z';
   Subtype Lower  is Character range 'a'..'z';
   Subtype Symbol is Character
     with Static_Predicate => Symbol in '&' | '@' | '?';
 
   Subtype Test_Character is Character
      with Static_Predicate  => Test_Character in Upper | Lower | Symbol,
           Predicate_Failure => Raise Constraint_Error;