Optimisation and unsafePerformIO

27 Oct 2002

      Consider the following program:

---------------------------------
{-# NOINLINE b #-}

b x  = if even x then unsafePerformIO getChar else bot

bot = bot

main = do
         putChar (b 4)
         putChar (b 6)

-----------------------------

when you compile the programm with the options: -O0
and execute the program you get:
...
test
ab      (That's the input)
ab      (That's the ouput)
when you compile the programm with the options: -O1 -fno-cse
you get:
...
test
ab
aa
my question is now: which transformation/optimisation is responsible for
that, and is it
possible to switch off this transformation?

David Sabel