Running a consumer inside a pipe
haskell, haskell-pipes
Solution
Something similar to your signature `Consumer i m o -> Pipe i o m r` could be done like this:
{-# LANGUAGE RankNTypes #-}
import Pipes
foo :: Monad m => Consumer' i m o -> Pipe i o m ()
foo consumer = consumer >>= yield
I have used the `Consumer'` polymorphic type synonym which, since it is not really closed "downstream", it can be used as a `Pipe` that never actually `yield`s. To make it yield the return value of the consumer, we simply use a monadic bind.
As for your `Consumer i m r -> Pipe i o m r` signature, it's simply the identity using the polymorphic type synonym:
iden :: Monad m => Consumer' i m r -> Pipe i o m r
iden consumer = consumer
Problem
I need to compose a consumer and a pipe so that the output of the consumer would feed the input of the pipe. I guess this could be solved with a combinator like this: ``` Consumer i m r -> (r -> Producer o m r') -> Pipe i o m r' ``` or this: ``` Consumer i m i' -> Pipe i' o m r -> Pipe i o m r ``` or a lifting function like the following: ``` Consumer i m r -> Pipe i o m r ``` or like this: ``` Consumer i m o -> Pipe i o m r ``` I tried doing `consumer >~ pipe` without a success. So how to approach this?