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From: "Martin Dowie" <martin.dowie@nospam.baesystems.com>
Newsgroups: comp.lang.ada
References: <9l7qon$d78$1@nntp9.atl.mindspring.net>
 <7E0e7.12187$vW2.6599957@news1.sttln1.wa.home.com>
 <9la73h$vvs$1@slb6.atl.mindspring.net>
Subject: Re: C-style 'union' in Ada?
Date: Tue, 14 Aug 2001 08:37:44 +0100
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Date: 2001-08-14T08:37:44+01:00
List-Id: <comp.lang.ada>

The trick (if you could call it that!) is to include a default value
for the discriminant in the type definition. You can then change its
value at will. If you don't have a default then you have to contraint
the object when you declare it - which then fixes it to that value.

Brian Catlin <briancatlin@mindspring.com> wrote in message
news:9la73h$vvs$1@slb6.atl.mindspring.net...
> I didn't know that a discriminant could be assigned at run time.  This is
close to what I want to do.
>
> Thanks!
>  -Brian
>
> "DuckE" <nospam_steved94@home.com> wrote in message
news:7E0e7.12187$vW2.6599957@news1.sttln1.wa.home.com...
[snip]
> > procedure string_demo is
> >
> >   type str_type is ( ansi, wide );
> >
> >   type string_desc( str_select : str_type := ansi ) is
> >     record
> >       case str_select is
> >         when ansi =>
> >           ansi_string : String_Access;
> >         when wide =>
> >           wide_string : Wide_String_Access;
> >       end case;
> >     end record;
> >
> > begin
> >   declare
> >     str : string_desc;
> >   begin
> >     str := ( str_select => ansi, ansi_string => new
String'( "Hello" ) );
> >     Free( str.ansi_string );
> >     str := ( str_select => wide, wide_string => new Wide_String'(
> > "There" ) );
> >     Free( str.wide_string );
> >   end;
> > end string_demo;
>