You would just change it like so.
S.mapM (\conn -> liftIO (getStr2 connection) >>= \b -> return (conn,b))
If you want to make it more brief, perhaps
{-# LANGUAGE TupleSections #-}
S.mapM(\conn = (conn,) <$> liftIO (getStr2 conn))
On Thu, Jun 8, 2017 at 10:57 AM, <aqua...@gmail.com> wrote:
> Hello, Group!
>
> I implemented a scheme (strN - stream N, a, b - items of stream):
>
> a -> b -> (a, b)
> a -> b -> (a, b)
> a -> b -> (a, b)
> . . ...
> str1 str2 str3
>
> i.e. from each item of str1 I get item of str2 (with network call) and then
> combine item from str1 and item from str2 to a pair - to analize combined
> item (because I need info from both items: a and b).
>
> In pseudocode:
>
> for a in str1Getter:
> b = getStr2 a
> analize(a, b)
>
>
> I done combining with S.zip from Streaming.Prelude. I suppose it's similar
> to Pipes and Conduits. And this looks like:
>
> (|>) = flip $
> str1Getter |> S.mapM (liftIO . getStr2 connection) |> S.zip str1Getter
>
> and sure here I got twice execution of str2 retrieving from network (each
> request happens twice), due this zip.
>
> Would somebody help me: how to make this scheme (in simple way)? I can pass
> a to getStr2 sure and to get from it not simple b but (a, b) but this looks
> not cool. Is some other way to do it?
>
>
> /Best regards, Paul
>
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