[mercury-users] Abstract instantiations?

[Fergus Henderson]

On 13-Dec-1999, Warwick Harvey <wharvey at cs.monash.edu.au> wrote:
> 
> I thought I'd read somewhere a while back that Mercury now supported 
> abstract instantiations.

Nope.

> I'm wondering whether I got confused between "abstract instantation 
> declarations" and "abstract instance declarations"

That seems likely.

> (I believe the latter _are_ supported).

Yes.

> I can't find them documented anywhere, and 
> trying to use them results in an error: e.g. if I put `:- inst foo.' in the 
> interface section, it complains there's no `=' in the declaration. 

The compiler does in fact have some experimental support for abstract
inst declarations in its source code (the syntax it uses is
`:- inst foo is private.', though knowing that won't help you much;
some compiler hacking would definitely be required...).
However, if you don't know anything about an inst, there's virtually
nothing that you can do with it.  So it's really an experiment that
failed.

The issues with abstract insts are pretty much the same as the
issues with polymorphic insts.

-- 
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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