[Haskell-beginners] [IO String] to IO [String]

[Ovidiu D]

Thanks.

I can see it working but I don't undestand why does untilexit actually stop
the processing. Can you explain that?

Also how could I display a prompt before reading each line?



On Mon, Apr 1, 2013 at 7:14 AM, Lyndon Maydwell <maydwell at gmail.com> wrote:

> Interact should be able to handle line-by-line interaction as per this
> example, it should even be able to handle the exit case thanks to laziness:
>
> > main :: IO ()
> > main = interact (unlines . map reverse . lines . untilexit)
> >
> > untilexit :: String -> String
> > untilexit ('e':'x':'i':'t':_) = []
> > untilexit (c:t)               = c : untilexit t
> > untilexit []                  = []
>
> There will be a lot of things that it won't be able to do however.
>
>
> On Mon, Apr 1, 2013 at 5:49 AM, Ovidiu D <ovidiudeac at gmail.com> wrote:
>
>> My problem with interact was that it doesn't give me the line when the
>> user hits enter but instead it gives me all the lines at once when stdin is
>> closed (unless I did something wrong)
>>
>> The other problem is that I want to stop the command processing when the
>> user types the command "exit" and it seems interact can't do that.
>>
>>
>> On Sun, Mar 31, 2013 at 2:52 PM, Lyndon Maydwell <maydwell at gmail.com>wrote:
>>
>>> Depending on what you're doing with the lines, it may be worth checking
>>> out the `interact` function as well :-)
>>>
>>>
>>> On Sun, Mar 31, 2013 at 7:42 PM, Kim-Ee Yeoh <ky3 at atamo.com> wrote:
>>>
>>>> On Sun, Mar 31, 2013 at 5:19 PM, Ovidiu D <ovidiudeac at gmail.com> wrote:
>>>> > I would like to make this function to have the signature
>>>> > f : IO [String]
>>>> > ...such that I can get rid of the IO monad and pass the pure string
>>>> list to
>>>> > the processing function.
>>>>
>>>> You could use:
>>>>
>>>> getContents >>= lines :: IO [String]
>>>>
>>>> -- Kim-Ee
>>>>
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