On Wed, 17 Sep 2008, Mitchell, Neil wrote:
I tend to use openFile, hGetContents, hClose - your initial readFile like call should be openFile/hGetContents, which gives you a lazy stream, and on a parse error call hClose.
I could use a function like withReadFile :: FilePath -> (Handle -> IO a) -> IO a withReadFile name action = bracket openFile hClose ... Then, if 'action' fails, the file can be properly closed. However, there is still a problem: Say, 'action' is a parser which produces a data structure lazily. Then further processing of that data structure of type 'a' may again stop before completing the whole structure, which would also leave the file open. We have to force users to do all processing within 'action' and to only return strict values. But how to do this?