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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012 Constraints (WRT an Ada IR)
Date: Tue, 29 Nov 2016 19:53:56 +0200
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:32512
Date: 2016-11-29T19:53:56+02:00
List-Id: <comp.lang.ada>

On 16-11-29 01:49 , Shark8 wrote:
> So, with Ada 2012 we gained some really nice possibilities
> with the way to express constraints, the downside is that
> there's now a fairly wide range of ways to express constraints on
> types. Obviously these differences must be accounted for, but
> the are functionally equivalent, for example:
>
> Subtype P0 is Natural range Natural'Succ(Natural'First)..Natural'Last;

This seems the same as Positive, to me.

> Subtype P1 is Integer range 1..Integer'Last;

And this is the standard definition of Positive.

> Subtype P2 is Integer
>     with Static_Predicate => P2 in 1..Integer'Last
>                           or else raise Constraint_Error;

Perhaps it was obvious to you, but this differs from Positive in that 
you cannot write P2'First or similar (illegal by RM 3.2.4(26/3)), but 
you can write Positive'First.

> Subtype P3 is Integer with
>   Static_Predicate  => P3 in 1..Integer'Last,
>   Predicate_Failure => raise Constraint_Error;

Same difference as for P2, I think.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .