[Haskell-beginners] What's the mean of >>=

[김명신]

I really appeciate your answer.
 
Thanks Again,
Myung
 
> Date: Mon, 20 Apr 2015 02:51:33 +0300
> From: rasen.dubi at gmail.com
> To: beginners at haskell.org
> Subject: Re: [Haskell-beginners] What's the mean of >>=
> 
> Hello!
> 
> >>= and >> are methods of Monad typeclass. Their meaning may be very different depending on the actual type. For IO >>= composes a new IO action which is, when executed, executes left action first and then passes its result to the right function.
> 
> So you can read
> putStr' xs >>= \ x -> putChar '\n'
> as "Execute action putStr' xs, then pass its result to \x -> putChar '\n'".
> 
> Many times the result of previous action is not used (as in above
> example), so there is >> which is like >>= but ignores the result of
> first action.
> It's something like
> x >> y = x >>= (\_ -> y)
> 
> So putStr' xs >> putChar '\n' is the same as putStr' xs >>= \ x -> putChar '\n'
> 
> This code can be rewritten in the do-notation as:
> do
>     putStr' xs
>     putChar '\n'
> 
> To summarize, for IO, >>= and >> are used to sequence actions.
> 
> Best regards,
> Alexey Shmalko
> 
> On Mon, Apr 20, 2015 at 2:33 AM, 김명신 <himskim at msn.com> wrote:
> > It could be stupid question because i'm very beginner of haskell.
> >
> > I found strange literals when i read haskell code.
> > Does anybody explan what the mean of >>= below ocode ? And additionally,
> > What is mean of >> itself?
> >
> > putStrLn' [] = putChar '\n'
> > putStrLn' xs - putStr' xs >>= \ x -> putChar '\n'
> >
> > putStr' [] = return ()
> > putStr' (x : xs) = putChar x >> putStr' n
> >
> > (because of i18n problem, back slash literal could be shown as '\')
> >
> > Thank you in advance
> > Myung Shin Kim
> >
> >
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