[Haskell-beginners] Trouble with formatting, Real World Haskell example

[Ed McCaffrey]

I hope the spacing is preserved by my email client; here's a formatting that
compiles:

import System.Environment (getArgs)

interactWith function inputFile outputFile = do
    input <- readFile inputFile
    writeFile outputFile (function input)

main = mainWith myFunction
    where mainWith function = do
            args <- getArgs
            case args of
              [input, output] -> interactWith function input output
              _ -> putStrLn "Usage: Interact inputFile outputFile"

myFunction = id

On Sat, Nov 22, 2008 at 9:53 PM, Robert Kosara <rkosara at gmail.com> wrote:

> I'm having some trouble getting the InteractWith example from Real World
> Haskell's Chapter 4 to compile. When I use spaces (like below), it says
> "Interact.hs:10:30: Empty 'do' construct." When I use tabs (4 spaces per
> tab), I get "Interact.hs:16:13: parse error on input `='." In either case, I
> don't see the problem. Any help would be greatly appreciated.
> I'm also confused about the formatting of the example in the book (page
> 72). The last line ("myFunction = id") seems to be indented between the
> where and the next line, why is that? Is that simply a layout problem? To
> me, it seems it should be on the same level as the where.
>
> Below is my program:
>
> -- Interact.hs, simple filter in Haskell
>
> import System.Environment (getArgs)
>
> interactWith function inputFile outputFile = do
>     input <- readFile inputFile
>     writeFile outputFile (function input)
>
> main = mainWith myFunction
>     where mainWith function = do
>         args <- getArgs
>         case args of
>             [input, output] -> interactWith function input output
>             _ -> putStrLn "Usage: Interact inputFile outputFile"
>
>         myFunction = id
>
>
> Regards,
>
> Robert
>
>
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
>


On Sat, Nov 22, 2008 at 10:41 PM, Ed McCaffrey <ed at edmccaffrey.net> wrote:

>
>
> On Sat, Nov 22, 2008 at 9:53 PM, Robert Kosara <rkosara at gmail.com> wrote:
>
>> I'm having some trouble getting the InteractWith example from Real World
>> Haskell's Chapter 4 to compile. When I use spaces (like below), it says
>> "Interact.hs:10:30: Empty 'do' construct." When I use tabs (4 spaces per
>> tab), I get "Interact.hs:16:13: parse error on input `='." In either case, I
>> don't see the problem. Any help would be greatly appreciated.
>> I'm also confused about the formatting of the example in the book (page
>> 72). The last line ("myFunction = id") seems to be indented between the
>> where and the next line, why is that? Is that simply a layout problem? To
>> me, it seems it should be on the same level as the where.
>>
>> Below is my program:
>>
>> -- Interact.hs, simple filter in Haskell
>>
>> import System.Environment (getArgs)
>>
>> interactWith function inputFile outputFile = do
>>     input <- readFile inputFile
>>     writeFile outputFile (function input)
>>
>> main = mainWith myFunction
>>     where mainWith function = do
>>         args <- getArgs
>>         case args of
>>             [input, output] -> interactWith function input output
>>             _ -> putStrLn "Usage: Interact inputFile outputFile"
>>
>>         myFunction = id
>>
>>
>> Regards,
>>
>> Robert
>>
>>
>> _______________________________________________
>> Beginners mailing list
>> Beginners at haskell.org
>> http://www.haskell.org/mailman/listinfo/beginners
>>
>>
>
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