I am trying to calculate the standard deviation for each index in a list of lists of floats. Using Ubuntu 18.04, ghc 8.0.2. I am getting the following runtime error which I have googled and still don't understand what "Integral Float" is exactly or even which parameter is causing the trouble. *Main> let z = stdDev 0 2 y x <interactive>:250:9: error: • Could not deduce (Integral Float) arising from a use of ‘stdDev’ from the context: Floating a bound by the inferred type of z :: Floating a => [a] at <interactive>:250:5-38 • In the expression: stdDev 0 (length (head (x))) y x In an equation for ‘z’: z = stdDev 0 (length (head (x))) y x Code: -- i is start index, l is length of each list, ms is list of means, -- xs is Matrix stdDev i l ms xs | i < l = sqrt(fromIntegral(sumOfMinusMeans i (ms!!i) xs) / fromIntegral(l)):(stdDev (i+1) l ms xs) | otherwise = [] --i is index, m is mean for the index sumOfMinusMeans i m (x:xs) | xs == [] = (x!!i - m)**2 | i < length x = (x!!i - m)**2 + (sumOfMinusMeans i m xs) | otherwise = 0 Types: *Main> :t stdDev stdDev :: (Floating a1, Floating a, Integral a1) => Int -> Int -> [a1] -> [[a1]] -> [a] *Main> :t sumOfMinusMeans sumOfMinusMeans :: (Eq t, Floating t) => Int -> t -> [[t]] -> t Variables: *Main> y [380.0,1.0] *Main> x [[600.0,1.0],[400.0,1.0],[170.0,1.0],[430.0,1.0],[300.0,1.0]]