On 16 Feb 2008, at 5:04 PM, Donn Cave wrote:
On Feb 16, 2008, at 3:46 PM, Philippa Cowderoy wrote:
On Sat, 16 Feb 2008, Alan Carter wrote:
I'm a Haskell newbie, and this post began as a scream for help.
Extremely understandable - to be blunt, I don't really feel that
Haskell
is ready as a general-purpose production environment unless users are
willing to invest considerably more than usual. Not only is it not as
"batteries included" as one might like, sometimes it's necessary
to build
your own batteries!
Ironically, the simple task of reading a file is more work than I
expect
precisely because I don't want to bother to handle exceptions. I
mean,
in some applications it's perfectly OK to let an exception go to
the top.
But in Haskell, you cannot read a file line by line without writing an
exception handler, because end of file is an exception! as if a
file does
not normally have an end where the authors of these library functions
came from?
I agree 100%; to make life tolerable around Haskell I/O, I usually
end up binding the moral equivalent of
tryJust (\ exc -> case exc of
IOException e | isEOFError e -> return ()
_ -> Nothing) $
getLine
somewhere at top level and then calling that where it's needed.
For the author of the original post ... can't make out what you
actually
found and tried, so you should know about "catch" in the Prelude, the
basic exception handler.
Also, you might need to know that bracket nests in various ways:
bracket openFile hClose $ bracket readLine cleanUpLine $ proceed
There's also finally, for when the first argument to bracket is
ommitted, and (>>) for when the second argument is :)
jcc
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