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From: "Brian Catlin" <briancatlin@mindspring.com>
Newsgroups: comp.lang.ada
Subject: Re: C-style 'union' in Ada?
Date: Mon, 13 Aug 2001 20:49:04 -0700
Organization: Sannas Consulting
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Date: 2001-08-14T03:49:05+00:00
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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...
> Here is a comparable definition (I put it in a small program to make sure it
> compiled :-)
> I didn't include a separate length field since you don't really need it with
> Ada.  The length of the string may be found using
> "str.ansi_string.all'length" or "str.wide_string.all'length".
>
> Note that a default descriminant is used for the record such that the type
> of the record may be changed dynamically at run time (by assigning the whole
> record).
>
>
> with Ada.Strings.Unbounded;  -- Defines String_Access and Free
>  use Ada.Strings.Unbounded;
> with Ada.Strings.Wide_Unbounded; -- Defines Wide_String_Access and Free
>  use Ada.Strings.Wide_Unbounded;
>
> 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;
>
>
> I hope this helps,
> SteveD