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From: Pascal Ledru <Ledru#m#_Pascal@MSMAIL3.HAC.COM>
Subject: Re: -ve values in enumeration rep clauses.
Date: 1996/06/14
Message-ID: <31C1C04A.4970@MSMAIL3.HAC.COM>#1/1
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references: <5c3p6DALoKwxEwb0@djcull.demon.co.uk>
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organization: Aerospatiale, Inc
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Date: 1996-06-14T00:00:00+00:00
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Obviously the range of your byte type should include negative values:

with Unchecked_Conversion;
with Text_IO;
procedure X is

  type A_Type is (A,B,C);

  for A_Type use
    ( A => -3,
      B => -2,
      C => -1 );

  for A_Type'Size use 8;

  --type Byte is new Integer range 0 .. 255;
  type Byte is new Integer range -126 .. 127;

  for Byte'Size use 8;

  function Convert is new Unchecked_Conversion
    ( Source => A_Type,
      Target => Byte );

begin
  Text_IO.Put_Line(Byte'Image( ( Convert(A) );
end;