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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Subtype predicates
Date: Wed, 24 Aug 2016 14:54:20 -0700
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On 08/24/2016 06:06 AM, AdaMagica wrote:
> Am Dienstag, 23. August 2016 22:14:30 UTC+2 schrieb Anh Vo:
>> type Human_Life_Span_Type is range 0 .. 130 
>>   with Default_Value => Human_Life_Span_Type'First;
> 
> No, I think it's the rule that the name of the entity declared in a declaration (here Human_Life_Span_Type) may not be used again in the same declaration. (You cannot use something that is to be defined recursively in the definition.)
> 
> I just cannot find the RM chapter and verse.

No, it's because of ARM 13.1.1(12/3): "If the associated declaration is a
type_declaration, within the aspect_definition ... the name of the first subtype
denotes the current instance of the type (see 8.6)." For a declaration:

V : Human_Life_Span_Type;

the current instance is V, so this says V's default value is V'First. Since you
can't apply 'First to a scalar object, the aspect is in error.

-- 
Jeff Carter
"He had no conception of the instrument. He
was blowing into it."
Take the Money and Run
135