Re: Q: unboxed values and polymorphism

[fjh@mundook.cs.mu.OZ.AU (Fergus Henderson)]

Hannes Haug <Hannes.Haug@Student.Uni-Tuebingen.de> writes:

>> "TT" == Tucker Taft <stt@henning.camb.inmet.com> writes:
>
>    TT> Tightly encoded variant records seem more likely to be the answer.
>
>But will this give me unboxed integers and type information on the stack ?

I'm no Ada expert, but I think that the theoretical answer is "it
depends on the compiler" and that the practical answer is that existing
Ada compilers won't be able to pack pointers and tag bits into a single
word.  (Ada afficionados, please correct me if I'm wrong!)

It's definitely possible for a compiler to do this sort of packing of
variant records; the compiler for Mercury does this in many cases.
(I know this because I wrote quite a bit of the code that does it ;-)

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