Haskell Language Design Questions

[Fergus Henderson]

On 29-Dec-2000, Doug Ransom <Doug_Ransom@pml.com> wrote:
> 1.  Is the lack of dynamic binding of functions by design or because it was
> too much effort to be justified at the time the language was designed?  In
> object oriented programming there can be several implementations of the same
> interface, and they can be stored in the same collection.

It's just something that didn't make it into Haskell 98.
Hugs and ghc offer a language extension for that.
It will almost certainly be in the next revision of Haskell.  See
<http://www.haskell.org/ghc/docs/latest/set/existential-quantification.html>.

> 2.	It seems to me that the Maybe monad is a poor substitute for
> exception handling because the functions that raise errors may not
> necessarily support it.

Hugs and ghc also have exception handling extensions.
See <http://www.haskell.org/ghc/docs/latest/set/sec-exception.html>.
There's also a paper or two on that.  I hope you'll forgive the
self-citation, but the only one for which I happen to have a reference
on-hand is this one:

	A semantics for imprecise exceptions. Simon Peyton-Jones,
	Alastair Reid, Tony Hoare, Simon Marlow, and Fergus Henderson.
	Proceedings of the 1999 ACM SIGPLAN Conference on Programming
	Language Design and Implementation, May 1999.

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