[Haskell-cafe] Re: Curious Functor Class
ashley at semantic.org
Thu Sep 28 03:59:27 EDT 2006
On Sep 28, 2006, at 00:38, Jeremy Gibbons wrote:
>> Perhaps the key is that there exist types P and Q s.t. there's an
>> F a <=> (P -> a,Q)
> F is Naperian iff there's a P with F a = P -> a; but what's the Q for?
>> This seems to be intuitively Napierian:
>> ln (P -> a,Q) = (P,ln a) | ln Q
>> I can believe that Hoistables are in fact Idioms, though I know
>> there are Idioms that are not Hoistables (Maybe and Either, for
> That's right. Every Monad is an Idiom. So are constant functors (F
> a = Int) - which I guess a Naperian anyway.
Hoistables are not always Idioms, it turns out. I think this can be
made a Hoistable, but not an Idiom (because it has a "Q"):
type WithInt = (,) Int -- i.e. WithInt a = (Int,a)
I don't know if that counts as Napierian or not.
>> (Also I think "Idiom" is a better class name than "Applicative".)
> Me too! Can you tell Ross and Conor? I've tried...
Hey Ross, Conor, "Idiom" is a better name than "Applicative". Pretty
much everyone thinks so.
> I don't subscribe to haskell-cafe, so apparently I can't post. Feel
> free to post my reply there, if you think it is useful.
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