I wrote:

darcs get "http://semantic.org/TimeLib/" ... I hope to get more implementation done this coming week.

I've done some more implementation, the basic calendric conversions work. Have a look, send me any comments/concerns or better yet reply here on the list. One thing I am considering is using a Fixed type (a possible Data.Fixed attached/appended) for DiffTime. This would make DiffTime an instance of Num etc. with 1 = 1 second rather than 1 = 1 picosecond, while still maintaining picosecond resolution (as Qrczak suggested). Opinions? Also, I've set -fglasgow-exts, mostly to get "cunning newtype" deriving. But presumably this lack of portability is undesirable? -- Ashley Yakeley, Seattle WA {-# OPTIONS -fglasgow-exts -Wall -Werror #-} module Data.Fixed ( Fixed,FixedResolution(..), E6,Micro, E12,Pico ) where newtype Fixed a = MkFixed Integer deriving (Eq,Ord,Enum) class FixedResolution a where fixedResolution :: a -> Integer instance (FixedResolution a) => Num (Fixed a) where (MkFixed a) + (MkFixed b) = MkFixed (a + b) (MkFixed a) - (MkFixed b) = MkFixed (a - b) (MkFixed a) * (MkFixed b) = MkFixed (div (a * b) (fixedResolution (undefined :: a))) negate (MkFixed a) = MkFixed (negate a) abs (MkFixed a) = MkFixed (abs a) signum (MkFixed a) = fromInteger (signum a) fromInteger i = MkFixed (i * fixedResolution (undefined :: a)) instance (FixedResolution a) => Real (Fixed a) where toRational (MkFixed a) = (toRational a) / (toRational (fixedResolution (undefined :: a))) instance (FixedResolution a) => Fractional (Fixed a) where (MkFixed a) / (MkFixed b) = MkFixed (div (a * (fixedResolution (undefined :: a))) b) recip (MkFixed a) = MkFixed (div ((fixedResolution (undefined :: a)) * (fixedResolution (undefined :: a))) a) fromRational r = MkFixed (floor (r * (toRational (fixedResolution (undefined :: a))))) instance (FixedResolution a) => RealFrac (Fixed a) where properFraction a = (i,a - (fromIntegral i)) where i = truncate a truncate f = truncate (toRational f) round f = round (toRational f) ceiling f = ceiling (toRational f) floor f = floor (toRational f) -- only works for positive a showIntegerZeros :: Int -> Integer -> String showIntegerZeros digits a = replicate (digits - length s) '0' ++ s where s = show a instance (FixedResolution a) => Show (Fixed a) where show (MkFixed a) | a < 0 = "-" ++ (show (MkFixed (negate a) :: Fixed a)) show (MkFixed a) = (show i) ++ "." ++ (showIntegerZeros digits fracNum) where f = fixedResolution (undefined :: a) (i,d) = divMod a f -- enough digits to be unambiguous digits = ceiling (logBase (fromInteger f) 10 :: Double) maxnum = 10 ^ digits fracNum = div (d * maxnum) f data E6 instance FixedResolution E6 where fixedResolution _ = 1000000 type Micro = Fixed E6 data E12 instance FixedResolution E12 where fixedResolution _ = 1000000000000 type Pico = Fixed E12