On Sun, 23 Sep 2007, Thomas Conway wrote:
In Prelude there is a function properFraction which splits a RealFrac into its integer part and its fractional part. You can use this to implement fmod. Assuming properFraction is efficient (which it probably isn't), you can implement fmod really quite efficiently.
In particular, x `fmod` 1.0 == (snd . properFraction) x
Unfortunately, properFraction doesn't work well with negative numbers. I get Prelude> properFraction (-0.3) (0,-0.3) but usually I need Prelude> properFraction (-0.3) (-1,0.7) Thus I defined a work-around:
splitFraction x = let (n,f) = properFraction x in if x>=0 || f==0 then (fromInteger n, f) else (fromInteger n-1, f+1)
See also http://www.haskell.org/haskellwiki/Things_to_avoid#Forget_about_quot_and_rem