Conal Elliott wrote:
Is there a simpler model of Enumerator? My intuition is that it's simply a
stream:
[[Enumerator a]] = String
Oddly, 'a' doesn't show up on the RHS. Maybe the representation ought to be
type Enumerator = forall a. Iteratee a -> Iteratee a
so
[[Enumerator]] = String
I concur, that seems to be all there is to it.
There is a small nuance in the Iteratee implementation, namely: if an
Enumerator is something that provides a complete input stream to an
Iteratee, why isn't it simply defined as
type Enumerator = forall a. Iteratee a -> a
i.e. as a function that runs an Iteratee on an input stream and extracts
the result? I think the purpose of the implementation
type Enumerator = forall a. Iteratee a -> Iteratee a
is that it allows us to concatenate different input streams. In other words
fromString (xs ++ ys) = fromString ys . fromString xs
assuming a function
fromString :: String -> Enumerator
To get an actual result from an Iteratee, we only need a way to run it
on the empty stream.
runOnEmptyString :: Iteratee a -> Maybe a
Regards,
Heinrich Apfelmus
--
http://apfelmus.nfshost.com
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