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From: mab@dst17.wdl.loral.com (Mark A Biggar)
Subject: Re: Two ideas for the next Ada Standard
Date: 1996/09/05
Message-ID: <50ms2p$4e4@wdl1.wdl.lmco.com>#1/1
X-Deja-AN: 178678857
references: <50gelc$2le@goanna.cs.rmit.edu.au> <Dx5zH4.2zo@world.std.com>
 <JSA.96Sep4172154@alexandria>
organization: Loral Western Development Labs
newsgroups: comp.lang.ada
Date: 1996-09-05T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <JSA.96Sep4172154@alexandria> jsa@alexandria (Jon S Anthony) writes:
>In article <Dx5zH4.2zo@world.std.com> bobduff@world.std.com (Robert A Duff) writes:
>> Another choice is to declare a root integer type, and declare the
>> function as primitive of that type, and inherit that function for all
>> your integer types.  But this requires everything to be derived from a
>> single root type, which inhibits code reuse.
>Interesting.  Care to elaborate (so to speak...)?

The original Ada9x (before the trim down) had the idea of allowing the use
of 'CLASS on non-tagged types for just this purpose.  E.g.  you could declare
a procedure like:

procedure My_Op(P1: Integer'CLASS; P2: in out Float'CLASS);

Valid parameter for P1 and P2 could be anything of a type derived from
Integer and Float respectively.  This is very similar to the above 
method but the compiler implisitely does the required conversions.

This would make a reasonably simple GNAT experimential extension.

--
Mark Biggar
mab@wdl.lmco.com