Will Haskell be commercialized in the future?

Tyson Dowd [email protected]
Tue, 28 Nov 2000 14:52:25 +1100


On 27-Nov-2000, Adrian Hey <[email protected]> wrote:
> On Mon 27 Nov, Fergus Henderson wrote:
> >  Do you think that Haskell would be better without `unsafePerformIO'?
> 
> Well, a sceptic like me is bound to wonder why such a non-function is
> provided in a purely functional language. What really worries me is
> that the damage isn't localised. If you allow such things you can never be
> sure that any function really is a function, without careful scrutiny of all
> the code it's dependent on.

This is an issue, but it arises in any "pure" language with a foreign
language interface.  

I think what would be nice to have is a notion of "trust".  Only "trusted"
people can use unsafePerformIO -- of course as the application developer
you can decide who you trust and who you don't trust.  It would be
possible to use public key crypto to handle trust (if you were worried
enough to bother).  Then you only have to scrutinze uses of
unsafePerformIO that you don't trust.

We have been thinking of adding some support for "safety", "purity" and
"trust" to Mercury for a while, but haven't quite hammered out exactly what
these concepts mean and how they interact (or even whether it is all
worthwhile).  The general idea is that you could trust :- promise pure
declarations (which are similar to unsafePerformIO).  There are other :-
promise declarations too.  To use a :- promise declaration you would
have to trust the author.

-- 
       Tyson Dowd           # 
                            #  Surreal humour isn't everyone's cup of fur.
     [email protected]        # 
http://www.cs.mu.oz.au/~trd #