----- Original Message ----- From: "Albert Lai" To: Sent: Wednesday, October 30, 2002 7:35 AM Subject: 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.

No! I used the option -fno-cse, what means that common supexpression elimination is turned off.

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