[Haskell-cafe] Basic question concerning the category Hask (was:
concerning data constructors)
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.
>>> (1) Must be monotone
>>> (2) Must be continuous
>>> (Needn't be strict, even though that messes up the resulting
>>> category substantially).
>> 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?
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