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module Utils.List exposing
( groupBy
, mean
)
import Dict
groupBy : (a -> comparable) -> List a -> List (comparable, List a)
groupBy f xs =
let addItem item dict =
let groupItems = Dict.get (f item) dict |> Maybe.withDefault []
in Dict.insert (f item) (item :: groupItems) dict
in List.foldr addItem Dict.empty xs
|> Dict.toList
mean : List Int -> Int
mean xs = (List.sum xs) // (List.length xs)
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