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35 changes: 10 additions & 25 deletions src/Data/List/Lazy.purs
Original file line number Diff line number Diff line change
Expand Up @@ -326,11 +326,8 @@ findIndex fn = go 0
findLastIndex :: forall a. (a -> Boolean) -> List a -> Maybe Int
findLastIndex fn xs = ((length xs - 1) - _) <$> findIndex fn (reverse xs)

-- | Insert an element into a list at the specified index, returning a new
-- | list or `Nothing` if the index is out-of-bounds.
-- |
-- | This function differs from the strict equivalent in that out-of-bounds arguments
-- | result in the element being appended at the _end_ of the list.
-- | Insert an element into a list at the specified index, or append the element
-- | to the end of the list if the index is out-of-bounds, returning a new list.
-- |
-- | Running time: `O(n)`
insertAt :: forall a. Int -> a -> List a -> List a
Expand All @@ -340,11 +337,8 @@ insertAt n x xs = List (go <$> unwrap xs)
go Nil = Cons x nil
go (Cons y ys) = Cons y (insertAt (n - 1) x ys)

-- | Delete an element from a list at the specified index, returning a new
-- | list or `Nothing` if the index is out-of-bounds.
-- |
-- | This function differs from the strict equivalent in that out-of-bounds arguments
-- | result in the original list being returned unchanged.
-- | Delete an element from a list at the specified index, returning a new list,
-- | or return the original list unchanged if the index is out-of-bounds.
-- |
-- | Running time: `O(n)`
deleteAt :: forall a. Int -> List a -> List a
Expand All @@ -354,11 +348,8 @@ deleteAt n xs = List (go n <$> unwrap xs)
go 0 (Cons y ys) = step ys
go n' (Cons y ys) = Cons y (deleteAt (n' - 1) ys)

-- | Update the element at the specified index, returning a new
-- | list or `Nothing` if the index is out-of-bounds.
-- |
-- | This function differs from the strict equivalent in that out-of-bounds arguments
-- | result in the original list being returned unchanged.
-- | Update the element at the specified index, returning a new list,
-- | or return the original list unchanged if the index is out-of-bounds.
-- |
-- | Running time: `O(n)`
updateAt :: forall a. Int -> a -> List a -> List a
Expand All @@ -369,22 +360,16 @@ updateAt n x xs = List (go n <$> unwrap xs)
go n' (Cons y ys) = Cons y (updateAt (n' - 1) x ys)

-- | Update the element at the specified index by applying a function to
-- | the current value, returning a new list or `Nothing` if the index is
-- | out-of-bounds.
-- |
-- | This function differs from the strict equivalent in that out-of-bounds arguments
-- | result in the original list being returned unchanged.
-- | the current value, returning a new list, or return the original list unchanged
-- | if the index is out-of-bounds.
-- |
-- | Running time: `O(n)`
modifyAt :: forall a. Int -> (a -> a) -> List a -> List a
modifyAt n f = alterAt n (Just <<< f)

-- | Update or delete the element at the specified index by applying a
-- | function to the current value, returning a new list or `Nothing` if the
-- | index is out-of-bounds.
-- |
-- | This function differs from the strict equivalent in that out-of-bounds arguments
-- | result in the original list being returned unchanged.
-- | function to the current value, returning a new list, or return the
-- | original list unchanged if the index is out-of-bounds.
-- |
-- | Running time: `O(n)`
alterAt :: forall a. Int -> (a -> Maybe a) -> List a -> List a
Expand Down