> Haskell doesn't really have "loops" weeell, you can still do stuff like this in Haskell: import Data.Vector.Mutable ... let n = length vec

> Haskell doesn't really have "loops" weeell, you can still do stuff like this in Haskell: import Data.Vector.Mutable ... let n = length vec forM_ [0 .. n-1] $ \i -> do next <- if i < n-1 then read vec (i+1) else pure 0 modify vec (+ next) i -- increase this value by next value it's just in many cases the functional machinery is so accessible that you don't need to reach for for-loops.