Hi,
Yes, yes, I know, I know. I shouldn't be using `unsafePerformIO'. But it
is so useful!
That it can completely mess up things shows the following (after a long
time tracked down to its bare essentials:)
-- begin code
module Bug where
import IOExts
main :: IO ()
main = writeFile "cat" buggy
buggy :: String
buggy = unsafePerformIO $
do writeFile "cow" "Animal Farm"
return "horse"
-- end code
After running `main', you get an "unexpected signal", and Hugs crashes.
The combination of the following two things causes the problem:
- the writing to a file of an unsafe string,
- that when evaluated writes to another file.
Either one of these things is no problem; if you (in the same hugs
session) first evaluate `buggy' (and the side effect is being performed),
and then type `main', everything works fine.
HBC has no problems with this.
Thanks,
Koen.
--
Koen Claessen,
[EMAIL PROTECTED],
http://www.cs.chalmers.se/~koen,
Chalmers University of Technology.
