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From: "Frank J. Lhota" <NOSPAM.Lhota.adarose@verizon.net>
Newsgroups: comp.lang.ada
References: <MtzFd.82780$C94.78656@tornado.fastwebnet.it>
Subject: Re: How unchecked conversion works?
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Message-ID: <iEBFd.612$qu2.222@trndny08>
Date: Thu, 13 Jan 2005 21:22:22 GMT
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Date: 2005-01-13T21:22:22+00:00
List-Id: <comp.lang.ada>

You would not use Unchecked_Conversion to convert a float to an integer. 
Basically, Unchecked_Conversion takes an object S of type Source and pretend 
it is an object of type Target, simply by assuming that an object of type 
Target resides at the same address as S. In other words, if we define

    function Convert is new Ada.Unchecked_Conversion( Source, Target );

    S : Source;

then the Ada call

    Convert( S )

does basically the same thing as the following C code:

    *( (Target *) &S )

Needless to say, the result of unchecked conversion depends heavily on the 
internal representation of the Source and Target types. This type of 
conversion is inherently risky in either C or Ada, which is why Ada makes it 
difficult to do unchecked conversions.

You almost certainly do not want to do an unchecked conversion to change a 
float into an integer. The integer resulting from such a conversion would 
have little to do with the original floating point number. Most likely you 
want to do a straighforward type conversion. For example:

    type My_Float is digits 6;
    type My_Integer is range 1 .. 10;

    S : My_Float;

Then we can convert S into a My_Integer value by writing

    My_Integer( S )

That's it!