2010/5/19 Erik de Castro Lopo
Dmitry Olshansky wrote:
It seems that I saw something like this in Cafe recevtly. But I am not sure... In GHC 6.12.1 (Platform 2010 on Windows Vista) I have
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Any comments?
The problem you point out is not a problem with Haskell, but a problem with the whole concept of floating point arithmetic as implemented on all modern CPUs. See:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
You would have got similar problems with just about any language running on the same hardware.
This is what used for Double list generation (Haskell Platform 2010): -------------------------------------------------- numericEnumFromThenTo :: (Ord a, Fractional a) => a -> a -> a -> [a] numericEnumFromThenTo e1 e2 e3 = takeWhile predicate (numericEnumFromThen e1 e2) where mid = (e2 - e1) / 2 predicate | e2 >= e1 = (<= e3 + mid) | otherwise = (>= e3 + mid) -------------------------------------------------- So normal C loop like for {double i = 1; i <= 10; i += 1+2/3) { insert_list(i); } won't generate the same list, as Haskell does in [1,1+2/3..10]. PS Rationals: Prelude> [1,1+2/3..10] :: [Rational] [1 % 1,5 % 3,7 % 3,3 % 1,11 % 3,13 % 3,5 % 1,17 % 3,19 % 3,7 % 1,23 % 3,25 % 3,9 % 1,29 % 3,31 % 3] Same result.