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Today's Topics:
1. Does Haskell work on Free BSD? (KC)
2. Re: Does Haskell work on Free BSD? (Mike Meyer)
3. Re: Haskeline and forkIO (Peter Jones)
4. Re: Haskeline and forkIO (Neeraj Rao)
----------------------------------------------------------------------
Message: 1
Date: Wed, 3 Sep 2014 06:01:18 -0700
From: KC <[email protected]>
To: Haskell Beginners <[email protected]>
Subject: [Haskell-beginners] Does Haskell work on Free BSD?
Message-ID:
<CAMLKXy=3eyPmpqMBz4VDff+o-heZtSSOi-yO=pcck1m1hqt...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Does Haskell work on Free BSD?
If not which is the better Linux to use?
--
--
Sent from an expensive device which will be obsolete in a few months! :D
Casey
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Message: 2
Date: Wed, 3 Sep 2014 08:12:01 -0500
From: Mike Meyer <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Does Haskell work on Free BSD?
Message-ID:
<CAD=7u2cv74hpttkhhm3ij1q7_kajku1089rzlkrlwjy97gu...@mail.gmail.com>
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Haskell works fine on FreeBSD. Both ghc and hugs are available from the
package system. Or you can install the Haskell Platform
(hs-haskell-platform) from it. There are also a variety of Haskell software
packages for development as well as end users.
On Wed, Sep 3, 2014 at 8:01 AM, KC <[email protected]> wrote:
> Does Haskell work on Free BSD?
>
> If not which is the better Linux to use?
>
> --
>
> --
>
> Sent from an expensive device which will be obsolete in a few months! :D
> Casey
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
>
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Message: 3
Date: Wed, 03 Sep 2014 10:24:55 -0600
From: Peter Jones <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] Haskeline and forkIO
Message-ID: <[email protected]>
Content-Type: text/plain
"Jeff C. Britton" <[email protected]> writes:
> That suggestion works.
> I will have to continue learning more about Monads.
I should have also mentioned that if you enable GHC warnings it should
tell you that having the `return` before `loop` is discarding the value
given to it.
> -----Original Message-----
> From: Beginners [mailto:[email protected]]
> Sent: Thursday, August 28, 2014 7:11 AM
> To: [email protected]
> Subject: Re: [Haskell-beginners] Haskeline and forkIO
>
> "Jeff C. Britton" <[email protected]> writes:
>> loop :: InputT IO ()
>> loop = do
>> maybeLine <- getInputLine "Enter a file to compress> "
>> case maybeLine of
>> Nothing -> return () -- user entered EOF
>> Just "" -> return () -- treat no name as "want to quit"
>> Just path -> do
>> return (runWorker path)
>> loop
>
> The other issue you're having is because `runWorker path` is an `IO
> ()` value but at the point where you use it in the code the type
> system wants an `InputT IO ()`. To try to satisfy the type system you
> used `return` to build a `InputT IO (IO ())` value, but that doesn't
> actually work (as you've noticed). Since `InputT` is a transformer
> you have an extra layer to work through and so need to *lift* your `IO
> ()` value into the `InputT IO` layer. Try this:
>
> -- Add this import
> import Control.Monad.IO.Class
>
> loop :: InputT IO ()
> loop = do
> maybeLine <- getInputLine "Enter a file to compress> "
> case maybeLine of
> Nothing -> return () -- user entered EOF
> Just "" -> return () -- treat no name as "want to quit"
> Just path -> do
> liftIO (runWorker path)
> loop
>
>
> You can think of `liftIO` as having this signature (in this context):
>
> liftIO :: IO () -> InputT IO ()
--
Peter Jones, Founder, Devalot.com
Defending the honor of good code
------------------------------
Message: 4
Date: Wed, 3 Sep 2014 12:51:50 -0400
From: Neeraj Rao <[email protected]>
To: Peter Jones <[email protected]>, The Haskell-Beginners Mailing
List - Discussion of primarily beginner-level topics related to
Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Haskeline and forkIO
Message-ID:
<camtpa6anidjp9y1bq_e0gvscxdcysx8baknzzpokyjcs4xo...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
As a Haskell beginner, I would also like to recommend HLint as a very
useful tool to catch these kinds of things.
On Sep 3, 2014 12:25 PM, "Peter Jones" <[email protected]> wrote:
> "Jeff C. Britton" <[email protected]> writes:
> > That suggestion works.
> > I will have to continue learning more about Monads.
>
> I should have also mentioned that if you enable GHC warnings it should
> tell you that having the `return` before `loop` is discarding the value
> given to it.
>
> > -----Original Message-----
> > From: Beginners [mailto:[email protected]]
> > Sent: Thursday, August 28, 2014 7:11 AM
> > To: [email protected]
> > Subject: Re: [Haskell-beginners] Haskeline and forkIO
> >
> > "Jeff C. Britton" <[email protected]> writes:
> >> loop :: InputT IO ()
> >> loop = do
> >> maybeLine <- getInputLine "Enter a file to compress> "
> >> case maybeLine of
> >> Nothing -> return () -- user entered EOF
> >> Just "" -> return () -- treat no name as "want to quit"
> >> Just path -> do
> >> return (runWorker path)
> >> loop
> >
> > The other issue you're having is because `runWorker path` is an `IO
> > ()` value but at the point where you use it in the code the type
> > system wants an `InputT IO ()`. To try to satisfy the type system you
> > used `return` to build a `InputT IO (IO ())` value, but that doesn't
> > actually work (as you've noticed). Since `InputT` is a transformer
> > you have an extra layer to work through and so need to *lift* your `IO
> > ()` value into the `InputT IO` layer. Try this:
> >
> > -- Add this import
> > import Control.Monad.IO.Class
> >
> > loop :: InputT IO ()
> > loop = do
> > maybeLine <- getInputLine "Enter a file to compress> "
> > case maybeLine of
> > Nothing -> return () -- user entered EOF
> > Just "" -> return () -- treat no name as "want to quit"
> > Just path -> do
> > liftIO (runWorker path)
> > loop
> >
> >
> > You can think of `liftIO` as having this signature (in this context):
> >
> > liftIO :: IO () -> InputT IO ()
>
> --
> Peter Jones, Founder, Devalot.com
> Defending the honor of good code
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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