Thank you David!
Have a nice weekand
четверг, 8 июня 2017 г., 18:07:47 UTC+3 пользователь David M написал:
>
> 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, <aqu...@gmail.com <javascript:>> 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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