2010/1/13 Lauri Pesonen <lauri.peso...@iki.fi>: > I provided a Java solution to a problem of returning the first digit > of an integer on StackOverflow and someone wondered if there were any > floating point point problems with the solution, so I though I'd > implement the algorithm in Haskell and run QuickCheck on it. > Everything works fine on GHCi, but if I compile the code and run the > test, it fails with -1000, 1000, -1000000. Any ideas why? > > In any case it seems that the commenter was right and there are some > subtle problems with my solution. I'd just like to know more > details...
Ok, I've figured out why the compiled version fails the check: main = putStrLn $ show $ logBase 10 1000 when compiled returns 2.9999999999999996 on my system (WinXp 32-bit) which then gets truncated to 2. So it seems that there's a precision difference between the compiled and the interpreted code. 'logBase 10 999' on the other hand produces exactly the same value in both cases. I expect this to be a known issue with floats. Sorry for the noise. -- ! Lauri _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
