NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/comp/lang/ada/3789

Text File | 1992-12-22 | 2.8 KB | 91 lines

Newsgroups: comp.lang.ada
Path: sparky!uunet!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!udecc.engr.udayton.edu!blackbird.afit.af.mil!usafa.af.mil!kirk!cwarack
From: [e-mail] (Chris Warack <sys mgr>)
Subject: Re: Novice Question on Record Representation
Message-ID: <[e-mail]>
Sender: cwarack@kirk (Chris Warack <sys mgr>)
Nntp-Posting-Host: kirk.usafa.af.mil
Organization: USAF Academy, CO
References:  <[e-mail]>
Date: Fri, 18 Dec 1992 00:22:21 GMT
Lines: 78

Why do you say, "of course" there is an error in this?  You should be able
to layout a private type just as easily as any other -- of course, you need
knowledge of that private type which you otherwise might not need; but, you're
using a rep clause so you must need it.

However, you may be getting an error if your machine's storage unit is a byte
(like most machines).  In this case, you are laying out field A to take bytes
0 and 1; field B takes bytes 2 and 3; field C starts with byte 1 again, thus
takes bytes 1,2,3, and 4.  Bytes 1,2,3 are already allocated, however.
That is an error.  If your storage unit is a long word (32 bits), this should
work...

-- Chris

In article <[e-mail]>, [e-mail] (Josh Lam) writes:
|> There is a type in another package I need to use in a record in my package.
|> Unfortunately, that type is private and I need to use record representation
|> for my record.
|>
|> package Some_Package is
|>
|>  type Some_Int is new integer;
|>  for Some_Int'size use 16;
|>
|>  type Some_Type is private
|>
|>  -- etc etc
|>
|>  private
|>
|>   type Some_Type is new integer;
|>   for Some_Type'size use 32;
|>
|> end Some_Package;
|>
|>
|> with Some_Package;
|> package My_Package is
|>
|>  type My_Rec (Choice: Boolean := True) is record
|>    case Choice is
|>      when True =>
|>        A : Some_Package.Some_Int;
|>        B : Some_Package.Some_Int;
|>        C : Some_Package.Some_Type;
|>      when False =>
|>        D : Some_Package.Some_Int;
|>    end case;
|>  end record;
|>
|>  for My_Rec use record
|>     A      at 0 range 0..15;
|>     B      at 0 range 16..31;
|>     C      at 1 range 0..31;     -- of course there is an error here!
|>     Choice at 2 range 0..31;
|>     D      at 0 range 0..15;
|>  end record;
|>
|> -- etc etc
|>
|> end My_Package;
|>
|>
|> I know that I cannot do the above cos C is of Some_Package.Some_Type which
|> is a private type.
|>
|> So, other than yelling at the person and getting him to change his type
|> to public, what are my alternatives given that I need to use record
|> representation. Please also let me know some pros and cons (if any) to any
|> alternative.
|>
|> Thanks in advance!
|>
|> --
|> Josh Lam
|> Honeywell Inc
|> [e-mail]
|>