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From: Alex Mentis <asmentis@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Min/Max attribute makes promises it can't keep
Date: Wed, 28 Apr 2010 03:36:40 -0700 (PDT)
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Date: 2010-04-28T03:36:40-07:00
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On Apr 27, 5:16=A0pm, Robert A Duff <bobd...@shell01.TheWorld.com>
wrote:
> Martin <martin.do...@btopenworld.com> writes:
> > =A0 =A0Put (Positive (Positive'Min(Nat, Pos)));
>
> That works, but I think a qualified expression is better:
>
> =A0 =A0Put (Positive'(Positive'Min(Nat, Pos)));
>
> By the way, there are lots of attributes that work
> like this (use the base subtype). =A0It's not just Min
> and Max.
>
> - Bob

I think you all missed my point: allowing the programmer to specify a
constraint in situations where the constraint will not be enforced
could cause confusion/error for someone who doesn't have the entire
ARM memorized....

Yes, I know there are ways to force Ada to do the check, like explicit
type conversion and qualified expressions.  That's pretty ugly,
though.  If I already have to put the type in front of the attribute,
why should I have to put the type in front of that again?  As long as
we're posting work-arounds, though, I suppose I would use the
following:

with Ada.Integer_Text_Io; use Ada.Integer_Text_Io;

procedure Main is

   function Min(Value_1, Value_2 : Integer) return Integer renames
Integer'Min;

   Nat : constant Natural :=3D 0;
   Pos : Positive;

begin

   Get (Pos);
   Put (Positive'(Min(Nat, Pos))); -- return a Positive result from
renamed Min else raise a Constraint_Error

end Main;