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From: "Matthew Heaney" <matthew_heaney@acm.org>
Subject: Re: Help me to chose between ADA 95 and C++
Date: 1999/12/14
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References: <01bf37fb$a91afb60$0564a8c0@IS-D2D04C.test>
 <B46461D2.259F%Harald.Schmidt@tomcat.de>
 <829rbv$a8m$1@nntp6.atl.mindspring.net> <01bf3e32$0b9dc880$022a6282@dieppe>
 <385112AE.7E2CFA9@rdel.co.uk> <833d8i$sjf$1@nntp5.atl.mindspring.net>
 <38566835.B4A2D48@rdel.co.uk> <8363hv$6cu$1@nntp9.atl.mindspring.net>
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Date: 1999-12-14T00:00:00+00:00
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In article <8363hv$6cu$1@nntp9.atl.mindspring.net> , Richard D Riehle 
<laoXhai@ix.netcom.com>  wrote:

> package Real_Number is
>   type Real is private;
>   function "+" (L, R : Real) return Real;
>   -- same for all other operators
>   Divide_By_Zero : exception;
>   -- more exceptions
> private
>   type Real is digits 9;
> end Real_Number;
>
> The corresponding package body can have additional checks within
> each operation to ensure conformity to the application constraints.
> It turns out, though, that implementing this, in Ada, is somewhat
> tedious because of the need to avoid recursive calls within each
> function in the package body.  It can be done.

Indeed it can.  You have a couple of possibilities:

1) Implement the full view of the type as a record containing a single
floating point component; or,

2) Implement the full view of the type as a private derivation, and do
type conversions in the body to convert between public and private views
of the type.