#37: Equal Ints are not equal ----------------------+----------------------------------------------------- Reporter: guest | Owner: ross Type: defect | Status: assigned Priority: blocker | Milestone: Component: hugs | Version: current Resolution: | Keywords: ----------------------+----------------------------------------------------- Old description:

Hi,

a few days ago I wrote a program which handles my own integers. Then I check my own implementation against the normal Int implementation in Hugs. Thereby I wonder about inequality of Ints which are definitely equal.

This is a test program I wrote after I recognized that hugs has probably a bug in the inequality check of Ints.

data MInt = Zero | Succ MInt | Pred MInt deriving Show

tn :: Int -> MInt tn x | x<0 = Pred (tn (x+1)) tn 0 = Zero tn (n+1) = Succ (tn n)

ti :: MInt -> Int ti Zero = 0 ti (Succ x) = 1+(ti x) ti (Pred x) = (ti x) -1

testi :: (MInt -> MInt -> MInt) -> (Int -> Int -> Int) -> Int -> Int -> Bool testi f g x y = (ti (f (tn x) (tn y))) /= (g x y)

myMul x y = tn ((ti x) * (ti y))

test = [(x,y,ti (myMul (tn x) (tn y)),x * y)| x<-[-100..100], y<-([-100..(-1)]++[1..100]),(testi myMul (*) x y) ]

the list "test" should be empty in any case but unfortunately hugs returns this (copy of the console):

__ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2003 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Report bugs to: hugs-bugs@haskell.org || || Version: November 2003 _________________________________________

Haskell 98 mode: Restart with command line option -98 to enable extensions

Type :? for help Main> test [(-100,80,-8000,-8000),(-100,99,-9900,-9900), (-99,58,-5742,-5742),(-99,83,-8217,-8217), (-98,71,-6958,-6958),(-98,86,-8428,-8428), (-97,46,-4462,-4462),(-97,87,-8439,-8439), (-96,76,-7296,-7296),(-95,88,-8360,-8360),(-94,73,-6862,-6862) ERROR - Control stack overflow Main>

I have checked this program with Hugs on different plattforms: Gentoo Linux x86 64-Bit and Suse Linux 32-Bit. On both plattforms the same bug occurs with different Ints for each run (i.e. the list contains different tuples). I have also checked my program with other Haskell implementations and there it returns an empty list as expected.

Best regards, Stephan Swiderski (swiderski@informatik.rwth-aachen.de)

P.S.: We have tested Sep2006 with similar results: __ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2005 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Bugs: http://hackage.haskell.org/trac/hugs || || Version: September 2006 _________________________________________

Haskell 98 mode: Restart with command line option -98 to enable extensions

Type :? for help Main> :e Main> test [(-100,90,-9000,-9000),(-98,40,-3920,-3920),(-97,63,-6111,-6111),(-97,69,-6693,- 6693) ERROR - Control stack overflow

New description: Hi, a few days ago I wrote a program which handles my own integers. Then I check my own implementation against the normal Int implementation in Hugs. Thereby I wonder about inequality of Ints which are definitely equal. This is a test program I wrote after I recognized that hugs has probably a bug in the inequality check of Ints. {{{ data MInt = Zero | Succ MInt | Pred MInt deriving Show tn :: Int -> MInt tn x | x<0 = Pred (tn (x+1)) tn 0 = Zero tn (n+1) = Succ (tn n) ti :: MInt -> Int ti Zero = 0 ti (Succ x) = 1+(ti x) ti (Pred x) = (ti x) -1 testi :: (MInt -> MInt -> MInt) -> (Int -> Int -> Int) -> Int -> Int -> Bool testi f g x y = (ti (f (tn x) (tn y))) /= (g x y) myMul x y = tn ((ti x) * (ti y)) test = [(x,y,ti (myMul (tn x) (tn y)),x * y)| x<-[-100..100], y<-([-100..(-1)]++[1..100]),(testi myMul (*) x y) ] }}} The list "test" should be empty in any case but unfortunately hugs returns this (copy of the console): {{{ __ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2003 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Report bugs to: hugs-bugs@haskell.org || || Version: November 2003 _________________________________________ Haskell 98 mode: Restart with command line option -98 to enable extensions Type :? for help Main> test [(-100,80,-8000,-8000),(-100,99,-9900,-9900), (-99,58,-5742,-5742),(-99,83,-8217,-8217), (-98,71,-6958,-6958),(-98,86,-8428,-8428), (-97,46,-4462,-4462),(-97,87,-8439,-8439), (-96,76,-7296,-7296),(-95,88,-8360,-8360),(-94,73,-6862,-6862) ERROR - Control stack overflow Main> }}} I have checked this program with Hugs on different plattforms: Gentoo Linux x86 64-Bit and Suse Linux 32-Bit. On both platforms the same bug occurs with different Ints for each run (i.e. the list contains different tuples). I have also checked my program with other Haskell implementations and there it returns an empty list as expected. Best regards, Stephan Swiderski (swiderski@informatik.rwth-aachen.de) P.S.: We have tested Sep2006 with similar results: {{{ __ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2005 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Bugs: http://hackage.haskell.org/trac/hugs || || Version: September 2006 _________________________________________ Haskell 98 mode: Restart with command line option -98 to enable extensions Type :? for help Main> :e Main> test [(-100,90,-9000,-9000),(-98,40,-3920,-3920),(-97,63,-6111,-6111),(-97,69,-6693,-6693) ERROR - Control stack overflow }}} -- Ticket URL: http://hackage.haskell.org/trac/hugs/ticket/37 Hugs http://www.haskell.org/hugs/ Hugs 98, an interpreter for Haskell

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