[m-dev.] subtyping proposal (repost)

[Fergus Henderson]

On 11-Feb-2000, Tyson Dowd <trd at cs.mu.OZ.AU> wrote:
> [Fergus wrote:]
> >                 :- type io__stream.
> >                         % abstract, but conceptually defined
> >                         % as follows:
> >                         % :- type io__stream --->
> >                         %               io__stream(
> >                         %               text_or_binary,
> >                         %               bool,   % input
> >                         %               bool,   % output
> >                         %               c_pointer).
> >                         % :- type text_or_binary ---> text ; binary.
>
> I'm a little unclear on what you mean in your proposal about 
> "abstract, but conceptually defined as follows".  What is the 
> Mercury syntax for conceptual definitions?

I meant that (1) the type was abstract; and (2) that it could be
defined as shown, but that this definition was just a specification,
and that the actual implementation might be different.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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