[Haskell-cafe] How to implement the mean function

[Ruohao Li]

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.
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