Re: [Haskell-cafe] How to implement the mean function

The problem is that you need to convert (length xs) to a Num, then return a Fractional. On Fri, Jul 1, 2011 at 2:07 PM, Nathan Howell wrote:

(/) 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 wrote:

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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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