Hello all,
the following program changes behavior if translated using different
options for ghc compiler. Is this correct or not? I used The Glorious
Glasgow Haskell Compilation System, version 6.6. And I would expect in
both cases behavior 1.
But I may be wrong...
Thanks for any resolution.
Dusan
*Program:*
$ cat Test.hs
import System.IO.Unsafe
import System.IO
main = do
putStr "Start...\n"
putStr $ show $ falling' falling10000
putStr "\n"
putStr $ show $ sorted' rising10000
putStr "Stop...\n"
sorted' [] = True
sorted' [_] = True
sorted' l = sx l 1
where
sx [] _ = True
sx [_] _ = True
sx (x:l@(y:ys)) n =
if n==1000 then unsafePerformIO (putChar '.' >> hFlush stdout)
`seq` x<=y && sx l 1
else x<=y && (sx l $! n+1)
falling' [] = True
falling' [_] = True
falling' l = sx l 1
where
sx [] _ = True
sx [_] _ = True
sx (x:l@(y:ys)) n =
if n==1000 then unsafePerformIO (putChar '.' >> hFlush stdout)
`seq` x>=y && sx l 1
else x>=y && (sx l $! n+1)
rising10000 = [0..100000]
falling10000 = [100000,99999..0]
-- EOF
*Behavior 1:*
$ ghc Test.hs -o test
$ ./test
Start...
....................................................................................................True
....................................................................................................TrueStop...
*Behavior 2:*
$ rm test Test.o Test.hi
$ ghc -O2 Test.hs -o test
$ ./test
Start...
.True
.TrueStop...
--
Dusan Kolar tel: +420 54 114 1238
UIFS FIT VUT Brno fax: +420 54 114 1270
Bozetechova 2 e-mail: [EMAIL PROTECTED]
Brno 612 66
Czech Republic
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