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From: okellogg <okellogg@users.sourceforge.net>
Newsgroups: comp.lang.ada
Subject: Should representation clauses be complete for each bit?
Date: Wed, 20 Jul 2011 03:34:23 -0700 (PDT)
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Date: 2011-07-20T03:34:23-07:00
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Picking up an age old thread,
http://groups.google.com/group/comp.lang.ada/browse_thread/thread/9ab165cd2cc73cb

IMHO it would be a real gain if we could explicitly mention the unused
bits in the rep spec.
Reusing the example from the OP,

>    type x is record
>      one : boolean;
>      two : boolean;
>      three : boolean;
>    end record;
>    for x use record
>      one   at 0 range 0..0;
>      two   at 0 range 3..3;
>      three at 0 range 15..15;
>    end record;

What I imagine is something like,

for x use record
   one   at 0 range 0 .. 0;
   null   at 0 range 1 .. 2;    // note reserved word "null"
   two   at 0 range 3 .. 3;
   null   at 0 range 4 .. 14;
   three at 0 range 15 .. 15;
end record;
for x'Size use 16;

The components with "null" would instruct the compiler to fill the
bits with 0.

-- Oliver