From: anon@anon.org (anon)
Subject: Re: Out parameters and unconstrained variant types
Date: Fri, 27 Jun 2008 00:49:16 GMT
Date: 2008-06-27T00:49:16+00:00 [thread overview]
Message-ID: <gOW8k.75717$102.66342@bgtnsc05-news.ops.worldnet.att.net> (raw)
In-Reply-To: c6f8a097-4675-4335-bbda-ae552be2e8e6@m73g2000hsh.googlegroups.com
--
-- Except for a few typos it work just fine in Ada 95 / 2005
-- using GNAT 3.15p and GNAT 2007 and 2008.
--
with Ada.Text_IO ;
use Ada.Text_IO ;
procedure Foo is
type Conditional_Result (Exists : Boolean := False) is record
case Exists is
when True => Value : Natural;
when False => null;
end case ;
end record;
procedure Do_Something(x : in Natural; rtn : out Conditional_Result) is
begin
if x = 0 then
rtn := (Exists => False);
else
rtn := (Exists => True, Value => x + 1);
end if;
end;
rtn : Conditional_Result;
begin
Do_Something(0, rtn);
if rtn.Exists then
Put_Line("Yes!");
end if;
Do_Something(1, rtn);
if rtn.Exists then
Put_Line("Yes!");
-- added to test value result.
Put_Line("Value" & Integer'Image( rtn.Value) );
end if;
end;
In <c6f8a097-4675-4335-bbda-ae552be2e8e6@m73g2000hsh.googlegroups.com>, Gene <gene.ressler@gmail.com> writes:
>Hello friends,
>
>I would like to do something like:
>
>type Conditional_Result (Exists : Boolean := False) is
> record case Exists is
> when True =>
> Value : Natural;
> when False => null;
> end record;
>
>procedure Do_Something(x : in Natural; rtn : out Conditional_Result)
>is
>begin
> if x = 0 then
> rtn := (Exists => False);
> else
> rtn := (Exists => True; Value => x + 1);
> end if;
>end;
>
>procedure Foo is
> rtn : Conditional_Result;
>begin
> Do_Something(0, rtn);
> if rtn.Exists then
> Put_Line("Yes!");
> end if;
> Do_Something(1, rtn);
> if rtn.Exists then
> Put_Line("Yes!");
> end if;
>end;
>
>ALRM 2005 and Barnes seem to say the procedure Do_Something will know
>that rtn in foo is unconstrained and allow both calls to succeed. In
>GNAT 2007, the second call fails with a constraint error at the
>assignment to rtn. Can you tell me what I'm missing?
>
>Thanks!
next prev parent reply other threads:[~2008-06-27 0:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-27 0:22 Out parameters and unconstrained variant types Gene
2008-06-27 0:49 ` anon [this message]
2008-06-27 2:40 ` Adam Beneschan
2008-06-27 7:11 ` Georg Bauhaus
2008-06-27 7:58 ` Dmitry A. Kazakov
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