elm baby steps

baby.elm

reduce : (a -> a -> a -> a) -> a -> Tree a -> a
reduce f base tree =
  case tree of
    Empty -> base
    Node v left right ->
      f v
        (reduce f base left)
        (reduce f base right)
        
sum tree =
  let f a b c = List.sum [a,b,c]
  in
    reduce f 0 tree