RMSE implementation in terms of fast vectors

example/Util/BMA.purs

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+module Example.Util.BMA where
+
+import Prelude
+
+import Data.FastVect.FastVect (Vect)
+import Data.Foldable (foldl)
+import Data.Int (toNumber)
+import Data.Number (pow)
+
+product :: forall a len. Semiring a => Vect len a -> a
+product v = foldl (*) one v 
+
+sum :: forall a len. Semiring a => Vect len a -> a
+sum v = foldl (+) zero v
+
+vlen :: forall a len. Vect len a -> Int
+vlen xs = foldl (\count _x -> (+) 1 count) 0 xs
+
+vlenN :: forall a len. Vect len a -> Number
+vlenN = toNumber <<< vlen
+
+mean :: forall len. Number -> Vect len Number -> Number
+mean 0.0 xs = product xs `pow` (1.0 / vlenN xs)
+mean p xs = (1.0 / vlenN xs * sum (map (pow p) xs)) `pow` (1.0/p)