Ralf Krueger wrote:
> I think, the problem can be solved by using the IO library and some
> strictness:
>
> import IO
>
> main = do text <- readFile "xxx"
> text' <- process $! text
> file <- openFile "xxx" WriteMode
> hPutStr file text'
> hClose file
>
> seems to work. The file will be read completly befor it is
> re-opened for writing.
Without trying it for myself, I have some doubts about the above code.
IIRC ($!) evaluates its second argument only to WHNF, i.e. only until
the toplevel constructor ((:) or [] in the case of lists) is known.
Perhaps you had luck because the files were short enough to fit into
the buffer of the underlying IO system. A more promising way is
probably:
main = readFile "xxx" >>= hyper >>= process >>= writeFile "xxx"
-- hack for hyperstrictness
hyper txt | length txt >= 0 = return txt
| otherwise = error "never happens"
And using hGetBuf{,BA}Full from GHC's upcoming IOExts module would be
a completely different way.
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Sven Panne Tel.: +49/89/2178-2235
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