[Haskell] [Haskell - I/O] Problem with 'readFile'

[John Hughes]

> Hello L.,
>
> Sunday, August 27, 2006, 12:43:24 PM, you wrote:
>
>>> >   length s `seq` writeFile f ("hello"++s)
>
>>   length mates_str `seq` return ()
>
> it's the same. i recommend you to use:
>
> return $! tail mates_str
>
> $! defined as
>
> f$!x = x `seq` f x
>
> 'tail' should be slightly faster than 'len'
>
> -- 
> Best regards,
> Bulat                            mailto:Bulat.Ziganshin at gmail.com

But you need to evaluate the result of readFile all the way to the end--you 
need to use a function that traverses the entire file contents. Otherwise 
the file will be left open to read the bit you haven't traversed. Hence 
length rather than tail.

John