comp hi xs =
  sum $ snd $ mapAccumL
    (\s (i, x) ->
        let
          (lts, ges@(Triple il _ _ : _)) =
            span (\(Triple _ x' _) -> x' < x) s
        in
          ( Triple i x il : ges
          , sum
              [ fromIntegral x' * fromIntegral (i' - il') * fromIntegral (i - i')
              | Triple i' x' il' <- lts
              ]
          )
    )
    [Triple 0 hi 0]
    (zip [1..] $ xs ++ [hi])

haskell-debug-adapter> <command line>: can't load framework: Cocoa (not found)