[Haskell-beginners] Trouble with formatting,
Real World Haskell example
ed at edmccaffrey.net
Sat Nov 22 22:41:29 EST 2008
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
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