[Haskell-cafe] GHC TV station?

[Sylvester Hazel]

Hi Victor,
It is frustrating that posting plain text is contorted (via nabble.com and
then again in my mail.google.com account) - please see the attachment.
I really have sent the right indentation copping the Hutton's script.
Is it so difficult for you guys to replicate this obvious failure of GHC on
"do notation" with white space?
Regards,
Sylvester

On Tue, May 15, 2018 at 6:27 PM, Viktor Dukhovni <ietf-dane at dukhovni.org>
wrote:

>
>
> > On May 15, 2018, at 12:13 PM, Sylvester via Haskell-Cafe <
> haskell-cafe at haskell.org> wrote:
> >
> > strlen in Hutton 2ed 10.5 Derived primitives => run on Windows 7 Haskell
> > Platform 8.2.2
> > strlen :: IO ()
> > strlen = do  putStr "Enter a string: "
> >                   xs <-  getLine
> >                   putStr "The string has "
> >                   putStr (show (length xs))
> >                   putStr " characters"
> > ===================================================
>
> The above indentation looks wrong.  Try:
>
> ----------
> $ cat foo.hs
> strlen :: IO ()
> strlen = do putStr "Enter a string: "
>             xs <-  getLine
>             putStr "The string has "
>             putStr (show (length xs))
>             putStrLn " characters"
>
> $ ghci foo.hs
> GHCi, version 8.0.2: http://www.haskell.org/ghc/  :? for help
> [1 of 1] Compiling Main             ( foo.hs, interpreted )
> Ok, modules loaded: Main.
> Loaded GHCi configuration from /tmp/haskell-stack-ghci/
> 05485125/ghci-script
> *Main> strlen
> Enter a string: foo
> The string has 3 characters
> *Main>
> ----------
>
> If I incorrectly indent the subsequent lines:
>
> strlen :: IO ()
> strlen = do putStr "Enter a string: "
>               xs <-  getLine
>               putStr "The string has "
>               putStr (show (length xs))
>               putStrLn " characters"
>
>
> Then I see an error:
>
> foo.hs:2:13: error:
>     Parse error in pattern: putStr
>     Possibly caused by a missing 'do'?
>
> --
>         Viktor.
>
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