Replace individual list elements in Haskell?

Question

I have a list of elements and I wish to update them:

from this: [\"Off\",\"Off\",\"Off\",\"Off\"]

to this: [\"Off\",\"Off\",\"On\",\"Off\

Answer 1

Here's some code that I've been using:

-- | Replaces an element in a list with a new element, if that element exists.
safeReplaceElement
  -- | The list
  :: [a]
  -- | Index of the element to replace.
  -> Int
  -- | The new element.
  -> a
  -- | The updated list.
  -> [a]
safeReplaceElement xs i x =
  if i >= 0 && i < length xs
    then replaceElement xs i x
    else xs


-- | Replaces an element in a list with a new element.
replaceElement
  -- | The list
  :: [a]
  -- | Index of the element to replace.
  -> Int
  -- | The new element.
  -> a
  -- | The updated list.
  -> [a]
replaceElement xs i x = fore ++ (x : aft)
  where fore = take i xs
        aft = drop (i+1) xs