Hi, you don't say what version of Hugs you're using, nor on what platform, but when I run your repro code with the Dec 2001 release on a Win2k box, the garbage collector runs out of heap space & complains. There are programs (and heap sizes) for which the garbage collector will blow the C stack, resulting in the kind of 'crash' which I believe you're experiencing. The Dec 2001 release did reduce the likelihood of that happening, so if you're not using it, I'd encourage you to pick it up. hth --sigbjorn ----- Original Message ----- From: <joosten@Anaxagoras.com> To: <hugs-bugs@haskell.org> Sent: Friday, January 04, 2002 02:47 Subject: (no subject)
I have performed research with Hugs quite a lot, and this is the first time I have run into a real bug. I have isolated the bug into the following program, which brings the Hugs interpreter down. Since an interpreter should be something that never "crashes" (it should generate error messages instead), I conclude that this must be a bug. Here is the program
testCycles rs = (paths, map shrink cycles) where shrink cycles = dropWhile (/=last cycles) cycles (paths, cycles) = f (rd[[a]| (a,b)<-rs, not (a `elem` map snd rs)], []) f (paths,cs) | null paths' = (paths,cs) | otherwise = f (paths++paths',cs++paths'') where paths' = rd[pth++[b]|pth<-paths, (a,b)<-rs, last pth==a, not (b `elem` pth)] paths'' = rd[pth++[b]|pth<-paths, (a,b)<-rs, last pth==a, b `elem` pth ]
rd [] = [] rd (x:xs) = x: rd [e|e<-xs, e/=x]
It crashes when executed. Try for example the expression:
testCycles [(1,4),(4,5),(7,8),(3,2),(2,7)]
Yours, Stef Joosten