CODEWITHSUNDEEP
haskell
CuriousCoder
CuriousCoder

Reputation: 1

How do I find the mean of a list in Haskell?

I'm trying to use one function to find the mean of a list in Haskell. This is what I put in: let listmean x = (foldl (+) 0x)/(length x) And I get this:

<`interactive>:43:18: error: • Could not deduce (Fractional Int) arising from a use of ‘/’ from the context: Foldable t bound by the inferred type of listmean :: Foldable t => t Int -> Int at :43:5-42 • In the expression: (foldl (+) 0 x) / (length x) In an equation for ‘listmean’: listmean x = (foldl (+) 0 x) / (length x)

I've tried to use the built-in div function but no luck there either. I run Haskell on https://replit.com, could it be the website?

Upvotes: 0

Views: 181

Answers (1)

j1-lee
j1-lee

Reputation: 13939

/ takes two Fractionals (try :info (/) in ghci). So you need to convert the Int into, say, Double:

main = print $ mean [0,1,1,2,3,5,8] -- 2.857142857142857

mean :: [Int] -> Double
mean xs = fromIntegral (sum xs) / fromIntegral (length xs)

Upvotes: 0

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