Catching IO errors doesn't seem to work in Hugs 1.4 (Jan98):
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
import IO (isDoesNotExistError)
main :: IO ()
main = catch (readFile "wibble" >>= \s -> putStr s)
(\e -> if isDoesNotExistError e
then putStr "File not found.\n"
else fail e)
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
when run with no file named "wibble" present produces:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Main> main
File or variable not found: wibble
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
and:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
import IO (isPermissionError)
main :: IO ()
main = catch (readFile "wibble" >>= \s -> putStr s)
(\e -> if isPermissionError e
then putStr "Not allowed.\n"
else fail e)
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
when run with an unreadable file named "wibble" present also produces:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Main> main
File or variable not found: wibble
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
hbc and ghc cope fine.
The alternative to catching is checking using the Directory 1.4
Library module but this does not appear to be present in Hugs 1.4?
Graeme.
