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