(/) operates on a Fractional instance... but length returns an Int, which is not a Fractional.
You can convert the Int to a Fractional instance: mean xs = sum xs / fromIntegral (length xs) or try an integer division: mean xs = sum xs `div` length xs -n On Thu, Jun 30, 2011 at 10:55 PM, Ruohao Li <liruo...@gmail.com> wrote: > Hi guys, > > I just started learning some Haskell. I want to implement a mean function > to compute the mean of a list. The signature of the function is: > mean :: (Num a, Fractional b) => [a] -> b > But when I implement this simple function, the compiler keep whining at me > on type errors. I know this is wrong: > mean xs = sum xs / length xs > But how to get it right? Thanks. > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >
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