At 5:31 am +1100 5/11/99, Fergus Henderson wrote:
>On 04-Nov-1999, Ronald J. Legere <[EMAIL PROTECTED]> wrote:
> >
> > If existential types are so natural [...] then
> > why arent they part of the types system from the get go?
>
>Implementing existential types is a non-trivial task.
Depends... If you restrict them in the same way universal quantification is limited in
typical Milner style systems then they're easy. We had them in Hope+C about 10 years
ago. See: <ftp://smis-asterix/ResearchPapers/ACSC15_Types.ps.Z> for some details.
[Note: Hope+C "hid" its existential types as syntax changes to the language were not
allowed - but such changes could have been made to make them easier to use, there was
no underlying restriction.]
Cheers,
Nigel
--
Dr Nigel Perry Email: [EMAIL PROTECTED]
IIST Tel: +64 6 350 5799 2477
Massey University Fax: +64 6 350 2259
Palmerston North FTP/WWW: smis-asterix.massey.ac.nz
New Zealand
It makes as much sense to wear a "cycle" style helmet in a car as on a bike...
Choosing to wear one on a bike but not in a car is mere inconsistency.
Refusing to wear one in a car while insisting others do so on a bike is pure hypocrisy.
Guess what the Minister of Transport does... :-(
Politics and hypocrisy before safety - the NZ Helmet Law, NZ's Shame
