Re: Some kind of repeating in Static_Predicate

["Randy Brukardt" <randy@rrsoftware.com>]

"ytomino" <aghia05@gmail.com> wrote in message 
news:503aed95-bd48-4eeb-a2a2-0f7bcc8de307@googlegroups.com...
> On Monday, June 4, 2018 at 3:26:56 PM UTC+9, Jacob Sparre Andersen wrote:
>> ytomino <agh...@gmail.com> writes:
>>
>> > I'm trying to use a constant table (but that is unstable and may be
>> > changed in compile-time) in Static_Predicate.
>> >
>> >  Set : constant String := ('T', 'a', 'b', 'l', 'e');
>> >
>> >  subtype T is Character
>> >     with Static_predicate => (for some I of Set => X = I);
>>
>> Why not admit that it is a Dynamic_Predicate?
>>
>> Alternatively:
>>
>>    type T is ('T', 'a', 'b', 'l', 'e');
>>
>> Or:
>>
>>    subtype T is Character
>>       with Static_Predicate => (T in 'T' | 'a' | 'b' | 'l' | 'e');
>>
>> Greetings,
>>
>> Jacob
>> -- 
>> "people who live in glass houses shouldn't be throwing rocks
>>  -- especially at those who don't live in glass houses"
>
> Thanks. But I want to separate the table and the subtype...

That seems backwards to me. You are wanting to declare a set subtype, and 
Ada uses the silly static predicate for doing so rather than having a proper 
set constraint. Either way, that's a subtype declaration.

So the operative thing here is the subtype. There's no "table" in a set 
description. If you need to check membership in the set, you just do that 
with "in".

Thus:

    subtype T is Character
       with Static_Predicate => (T in 'T' | 'a' | 'b' | 'l' | 'e');

    if Param in T then ...

If you really needed a table, I'd construct that from the set. (But I can't 
imagine what the use would be, certainly in cases like the "separators" 
definition you showed in another mail.)

                                  Randy.