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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: calenday (was Re: IBM Acquires Rational Ada
Date: Fri, 20 Dec 2002 15:29:57 -0600
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Frank J. Lhota wrote in message ...
>"Hyman Rosen" <hyrosen@mail.com> wrote in message
>news:1040410199.497867@master.nyc.kbcfp.com...
>> The whole concept of representation specs on tagged
>> records seems pretty dodgy to me.
>
>I agree. AFAIK, the only reason to use a representation clause is to
make
>sure that a type matches some external data layout. Tagged types, by
their
>very nature, do not fit into this category. This seems to be one of
those
>theoretical issues with no practical consequences.


Not true. It's perfectly possible to use rep. clauses to insure storage
minimization better than the compiler's pragma Pack. (Usually, Pack
assumes some amount of efficiency is required.)

Also, it is perfectly possible to pass a tagged record to an external
data layout, if that layout includes a tag already (such as COM on
Microsoft machines), or if you are passing the object minus the tag to
the external system, but need type extension to define the external
format properly (that's what happened to use with bitmaps in Claw).

I agree this isn't likely to be a common use, but it has happened, and I
understand that Rational finds that they have customers which think
these capabilities are very important. It's best not to argue with
customers. :-)

              Randy.