[Haskell-cafe] Re: (flawed?) benchmark : sort

Conor McBride conor at strictlypositive.org
Thu Mar 13 19:06:16 EDT 2008


On 13 Mar 2008, at 22:28, ajb at spamcop.net wrote:

> G'day all.
> Quoting Adrian Hey <ahey at iee.org>:
>> 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


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