[Haskell-cafe] how to write a pipes Consumer which return a final state

[PICCA Frederic-Emmanuel]

Hello, I try to create a pipes which return at the end a Cube.

the process is quite simple
1) extract data from a file
2) comput a cube of data from these data
3) accumulate these cube during the process
4) when there is no more cube return the final cube

I am trying for now to write the part with the 'state' which is hiden in a recursion like this.

accumulateP :: (MonadIO m, Shape sh)
            => Cube sh -> Consumer (DataFrameSpace sh) m (Cube sh)
accumulateP cube = do
  s <- await
  accumulateP =<< (liftIO $ addSpace s cube)

the add Space method return the modified Cube

At some point I should see that await can not return a value and
I would decide to return the value instead of doing another loop

My question is how do I stop this recursion and return the final cube ?

thanks for your help.