Hello!
I have a program that is using ST.Strict, which works fine.
However, the program needs to be extended, and to do that,
lazy evaluation is needed. As a result of that, I have switched
to ST.Lazy to be able to do stuff like
foo y = do
x <- something
xs <- foo (y+1)
return (x:xs)
However, when running the program compiled with ST.Lazy, the
following is outputted:
[to...@wobsi]$ ./runnerLazy looper.hex
runnerLazy: <<loop>>
The very same program compiled with ST.Strict outputs:
[to...@wobsi]$ ./runner looper.hex
83298556
The code that is actually computing stuff is this:
loopSys :: Int -> CPU s Int
loopSys cc = do
instr <- fetch
if instr == 0xEA --NOP
then return cc
else do
c <- execute instr
loopSys $! (cc+c)
The CPU type looks as follows:
type CPU s a = ReaderT (SysEnv s) (ST s) a
The program is run like
runReaderT (loopSys 0)
which in turn is being runST'd and then printed
Does anyone know why the program just outputs <<loop>>
when compiled under ghc 6.10.2, and runs perfectly fine
under ghc 6.8.2? The program is compiled with --make and -O2
Tobias Olausson
tob...@gmail.com
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