[Haskell-cafe] Basic question concerning the category Hask (was: concerning data constructors)

Yitzchak Gale gale at sefer.org
Sat Jan 5 21:03:06 EST 2008

Jonathan Cast wrote:
>>> The normal view taken by Haskellers is that the denotations of
>>> Haskell types are CPPOs.
>>>  So:
>>> (1) Must be monotone
>>> (2) Must be continuous
>>> (Needn't be strict, even though that messes up the resulting
>>> category substantially).

I wrote:
>> I'm not convinced that the category is all that "messed up".

> Well, no coproducts (Haskell uses a lifted version of the coproduct
> from CPO).

What goes wrong with finite coproducts? The obvious thing to
do would be to take the disjoint union of the sets representing the
types, identifying the copies of _|_.

What is the lifted version you are referring to?

>  Of course, Haskell makes things even worse by lifting the
> product and exponential objects,

OK, what goes wrong there, and what is the lifting?


More information about the Haskell-Cafe mailing list