Existentials

Malcolm Wallace Malcolm.Wallace@cs.york.ac.uk
Thu, 17 Apr 2003 16:16:34 +0100


"Simon Marlow" <simonmar@microsoft.com> writes:

> > The example I tried failed, so I assumed it wasn't supported.
> 
> You've written an existential constructor.  For universal
> quantification, write it like this:
> 
>    data T = Foo (forall a . Enum a => a -> a)
> 
> a good illustration of the confusion caused by the dual use of forall, I
> guess :-)

Exactly so.  :-)  If we change the syntax of existentials, would it
be possible to write my local universal example as I did originally
and have it work as expected?  Or will it still be necessary to push
the quantifier inside the constructor?

Regards,
    Malcolm