If I understand the question correctly, what you're saying is:

* My upstream (testC) is both returning a result _and_ yielding a stream of values downstream

* My downstream (CL.consume) is collecting those values and returning a result based on them

* How can I capture both the upstream and downstream results?

If so, this is the section of the docs with the relevant functions[1]. It provides a few different fusion functions to combine an upstream and downstream without throwing away the upstream result (which is the default behavior of conduit, for various design and usability reasons). In your case, this may look something like:

runConduit (fuseBoth testC CL.consume)

Michael

[1] https://s3.amazonaws.com/haddock.stackage.org/lts-6.3/conduit-1.2.6.6/Data-Conduit.html#g:4

On Wed, Jun 15, 2016 at 8:53 AM, <bruno@ruomad.net> wrote:

Hello,
I'm trying to use Data.Conduit, but I get stuck with mapAccum as how to get and retrieve the result.
If I use it, I get a simple conduit like :

testC :: ConduitM () Int IO Int
testC = Src =$= cdt where
src = CL.sourceList [1..10]
cdt = CL.mapAccum (\x s -> (x+s, x) 0

I can get the output with
testC $$ CL.consume
but how do I retrieve the accumulated sum ?

Bruno

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