Hi
On 13 Mar 2008, at 22:28, [EMAIL PROTECTED] wrote:
G'day all.
Quoting Adrian Hey <[EMAIL PROTECTED]>:
What's disputed is whether or not this law should hold:
(a == b) = True implies a = b
Apart from possibly your good self, I don't think this is disputed.
Quotient types, as noted elsewhere in this thread, are very useful.
For a suitable notion of = on quotients, and with a
suitable abstraction barrier at least morally in place,
is that really too much to ask?
Their common use predates Miranda, so it's way too late to unbless
them now.
How depressing! Untyped programming also predates
Miranda. We can always aspire for better. It's not
that we need to get rid of Quotients: it's just that
we need to manage information hiding properly, which
is perhaps not such a tall order.
Meanwhile, the sort/Ord/OrdWrap issue may be a storm
in a different teacup: the type of sort is too tight.
Ord (total ordering) is way too strong a requirement
for sorting. Antisymmetry isn't needed for sorting
and isn't possessed by OrdWrap. A bit more structure
for order-related classes would surely help here.
Isn't there room for hope?
All the best
Conor
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
