Re: Optimisation and unsafePerformIO

"David Sabel" writes:

{-# NOINLINE b #-}

b x = if even x then unsafePerformIO getChar else bot

bot = bot

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

I am not a compiler implementer (or lawyer, for that matter :) But I propose this guess. First, both even 4 and even 6 get constant-folded to True; so b 4 and b 6 both become unsafePerformIO getChar. Then there is a common subexpression elimination.