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From: Xavier Petit <xpetit@becoast.fr>
Subject: Predicate and value attribute
Date: Sat, 23 Jan 2016 12:16:10 +0100
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Xref: news.eternal-september.org comp.lang.ada:29208
Date: 2016-01-23T12:16:10+01:00
List-Id: <comp.lang.ada>

Hello, I have some beginner questions.

subtype Number is String
   with Dynamic_Predicate => Positive'Value (Number) in -1 | 5;

This line compiles and works. I would like some confirmation that 'Value 
attribute returns in this case the type Integer and doesn't take into 
account Positive subtype, and is why the following is valid:

Test : Number := "-1";

So I should never write "Positive'Value" right ?

And now my real newbie question : why do I have the error "Value_Integer 
is undefined" if I switch '|' to ".." this way :

subtype Number is String
   with Dynamic_Predicate => Positive'Value (Number) in -1 .. 5;

Knowing it works like this :

function Check (Item : String) return Boolean
is
   (Positive'Value (Item) in -1 .. 5);

subtype Number is String
   with Dynamic_Predicate => Check (Number);


Anyway now I use the oldschool :

type Number is range -1 .. 5;

and then do the conversion as string when I need to :

Number'Image (Item).

I could write a function to remove the first whitespace in case of 
non-negative number.

Thanks by advance !

-- 
Xavier Petit