Yield in your producer is of type DataFrameHkI3D -> Producer DataFrameHkl3D IO () But you are putting an (IO DataFrameHkI3D) in as an argument. You should be able to do something like this: getDataFrameHkl3D :: DataFrameHkl3DH5SixsUhv -> Producer DataFrameHkl3D IO () getDataFrameHkl3D d = do n <- lift $ hkl_h5_len (h5mu d) frames <- forM [0..n] $ \i -> lift (getDataFrameHkl3D' d i) -- :: Producer DataFrameHkl3D IO [DataFrameHkl3D] forM_ frames yield I have a feeling it may be more efficient to yield immediately on each loop as such: getDataFrameHkl3D :: DataFrameHkl3DH5SixsUhv -> Producer DataFrameHkl3D IO () getDataFrameHkl3D d = do n <- lift $ hkl_h5_len (h5mu d) forM_ [0..n] (\i -> lift (getDataFrameHkl3D' d i) >>= yield) You may also substitutde liftIO for lift, if you wish. On Tue, Mar 22, 2016 at 12:37 PM, PICCA Frederic-Emmanuel < frederic-emmanuel.picca@synchrotron-soleil.fr> wrote:

Hello,

Still playing with the Pipe module

here the code I try to write

getDataFrameHkl3D' :: DataFrameHkl3DH5SixsUhv -> Int -> IO DataFrameHkl3D getDataFrameHkl3D' d i = do positions <- get_position (h5mu d) i return $ DataFrameHkl3D { df_n = i , df_image = positions }

getDataFrameHkl3D :: DataFrameHkl3DH5SixsUhv -> Producer DataFrameHkl3D IO () getDataFrameHkl3D d = do n <- lift $ hkl_h5_len (h5mu d) forM_ [0..n] $ \i -> yield $ getDataFrameHkl3D' d i

but when I compile it I get this error message

src/hkl3d.hs:274:3: Couldn't match type `IO DataFrameHkl3D' with `DataFrameHkl3D' Expected type: Proxy X () () DataFrameHkl3D IO () Actual type: Proxy X () () (IO DataFrameHkl3D) IO () In a stmt of a 'do' block: forM_ [0 .. n] $ \ i -> yield $ getDataFrameHkl3D' d i In the expression: do { n <- lift $ hkl_h5_len (h5mu d); forM_ [0 .. n] $ \ i -> yield $ getDataFrameHkl3D' d i } In an equation for `getDataFrameHkl3D': getDataFrameHkl3D d = do { n <- lift $ hkl_h5_len (h5mu d); forM_ [0 .. n] $ \ i -> yield $ getDataFrameHkl3D' d i }

I do not know how to fix my code...

Frederic _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners