iteratee Couple functions for combining Enueratees with Enumerators and Iteratees

[Michael Baikov]

I never used enumerator package actually so I don't know :) Just make
sure that you add proper version of ($=), the one with forall.

Btw, there is something wrong with maillist. I don't see this
conversation in maillist archives on the website for example.

On Fri, Nov 25, 2011 at 7:02 PM, John Lato <jwlato at gmail.com> wrote:
> I've been meaning to add these for a while actually; I should be able
> to upload a new version after work today.
>
> Would you have any objection to using the same fixities as in the
> enumerator package?
>
> John L.
>
> On Fri, Nov 25, 2011 at 6:55 AM, Michael Baikov <manpacket at gmail.com> wrote:
>> One more version, clean on typelevel and without unsafeCoerce
>>
>>
>> ($=) :: (Nullable s1, Nullable s2, Monad m) => (forall a. Enumerator
>> s1 m a) -> Enumeratee s1 s2 m b -> Enumerator s2 m b
>> ($=) enum enee iter = enum (enee iter) >>= run
>>
>>
>> On Fri, Nov 25, 2011 at 2:14 PM, Michael Baikov <manpacket at gmail.com> wrote:
>>> Currently we have two nice functions for combining Enumeratees ><> and
>>> <>< which can be used to produce chains of Enumeratees. I think that
>>> it will be nice to have those functions as well:
>>>
>>>
>>> -- this implementation relies on unsafeCoerce to keep type signature
>>> nice and clean
>>> -- so it is requred to import Unsafe.Coerce
>>>
>>> --| Combines Enumerator which produces stream of s and Enumeratee
>>> which transforms stream of s to stream
>>> -- of s' to into Enumerator which produces stream of s'
>>> ($=) :: (Nullable s, Nullable s', Monad m) => Enumerator s m a ->
>>> Enumeratee s s' m b -> Enumerator s' m b
>>> ($=) enum enee iter = (unsafeCoerce enum) (enee iter) >>= run
>>>
>>>
>>>
>>> -- this implementation leaves type signature a bit messy, but without
>>> using unsafeCoerce
>>>
>>> --| Combines Enumerator which produces stream of s and Enumeratee
>>> which transforms stream of s to stream
>>> -- of s' to into Enumerator which produces stream of s'
>>> ($=) :: (Nullable s, Nullable s', Monad m) => Enumerator s m (Iteratee
>>> s' m a) -> Enumeratee s s' m a -> Enumerator s' m a
>>> ($=) enum enee iter = enum (enee iter) >>= run
>>>
>>>
>>> --| Combines Enumeratee from s to s' and Iteratee which consumes s' to
>>> into Iteratee which consumes s
>>> (=$) :: (Nullable s, Nullable s', Monad m) => Enumeratee s s' m a ->
>>> Iteratee s' m a -> Iteratee s m a
>>> (=$) = (.) joinI
>>>
>>>
>>> (=$) is mostly to keep sources clean, but ($=) can be used to
>>> enumerate any given Iteratee over list of several different data
>>> sources
>>> (but type of the source can be transformed to type of Iteratee using
>>> Enumeratee) just by transforming them to a single type and performing
>>> foldM.
>>>
>>
>