Re: [Haskell-cafe] Strange behaviour with writeFile

Hi Neil,

When you add that extra line the act of writing out the remainer causes the rest of the input to be fully evaluated and hence the filehandle is closed.

Ah, yes of course :) I've found that: let (answer2, remainder) = parseAnswer (force answer) where force :: Eq a => a -> a force x = if x==x then x else x Seems to do the trick. Thanks! Chris.

On 04/02/07, C.M.Brown wrote:

...

Hi,

I am observing some rather strange behaviour with writeFile.

Say I have the following code:

answer <- AbstractIO.readFile "filename" let (answer2, remainder) = parseAnswer answer if remainder == "" && answer2 == "" then do AbstractIO.putStrLn $ "completed" else do AbstractIO.putStrLn answer2 AbstractIO.writeFile "filename" remainder

With the above I get an error saying the resources to "filename" are locked. If I add the line "AbstractIO.putStrLn $ show (answer2, remainder) before I call writeFile it suddenly magically works!

Has anyone seen strange behaviour like this before?

Regards, Chris. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe