    {-# LANGUAGE Trustworthy #-} -- can't use Safe due to IsList instance
    {-# LANGUAGE TypeFamilies #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.List.NonEmpty
    -- Copyright   :  (C) 2011-2015 Edward Kmett,
    --                (C) 2010 Tony Morris, Oliver Taylor, Eelis van der Weegen
    -- License     :  BSD-style (see the file LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  provisional
    -- Portability :  portable
    --
    -- A 'NonEmpty' list is one which always has at least one element, but
    -- is otherwise identical to the traditional list type in complexity
    -- and in terms of API. You will almost certainly want to import this
    -- module @qualified@.
    --
    -- @since 4.9.0.0
    ----------------------------------------------------------------------------

    module Data.List.NonEmpty (
       -- * The type of non-empty streams
         NonEmpty(..)

       -- * Non-empty stream transformations
       , map         -- :: (a -> b) -> NonEmpty a -> NonEmpty b
       , intersperse -- :: a -> NonEmpty a -> NonEmpty a
       , scanl       -- :: Foldable f => (b -> a -> b) -> b -> f a -> NonEmpty b
       , scanr       -- :: Foldable f => (a -> b -> b) -> b -> f a -> NonEmpty b
       , scanl1      -- :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
       , scanr1      -- :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
       , transpose   -- :: NonEmpty (NonEmpty a) -> NonEmpty (NonEmpty a)
       , sortBy      -- :: (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
       , sortWith      -- :: Ord o => (a -> o) -> NonEmpty a -> NonEmpty a
       -- * Basic functions
       , length      -- :: NonEmpty a -> Int
       , head        -- :: NonEmpty a -> a
       , tail        -- :: NonEmpty a -> [a]
       , last        -- :: NonEmpty a -> a
       , init        -- :: NonEmpty a -> [a]
       , singleton   -- :: a -> NonEmpty a
       , (<|), cons  -- :: a -> NonEmpty a -> NonEmpty a
       , uncons      -- :: NonEmpty a -> (a, Maybe (NonEmpty a))
       , unfoldr     -- :: (a -> (b, Maybe a)) -> a -> NonEmpty b
       , sort        -- :: Ord a => NonEmpty a -> NonEmpty a
       , sortOn      -- :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
       , reverse     -- :: NonEmpty a -> NonEmpty a
       , inits       -- :: Foldable f => f a -> NonEmpty [a]
       , inits1      -- :: NonEmpty a -> NonEmpty (NonEmpty a)
       , tails       -- :: Foldable f => f a -> NonEmpty [a]
       , tails1      -- :: NonEmpty a -> NonEmpty (NonEmpty a)
       , append      -- :: NonEmpty a -> NonEmpty a -> NonEmpty a
       , appendList  -- :: NonEmpty a -> [a] -> NonEmpty a
       , prependList -- :: [a] -> NonEmpty a -> NonEmpty a
       -- * Building streams
       , iterate     -- :: (a -> a) -> a -> NonEmpty a
       , repeat      -- :: a -> NonEmpty a
       , cycle       -- :: NonEmpty a -> NonEmpty a
       , unfold      -- :: (a -> (b, Maybe a)) -> a -> NonEmpty b
       , insert      -- :: (Foldable f, Ord a) => a -> f a -> NonEmpty a
       , some1       -- :: Alternative f => f a -> f (NonEmpty a)
       -- * Extracting sublists
       , take        -- :: Int -> NonEmpty a -> [a]
       , drop        -- :: Int -> NonEmpty a -> [a]
       , splitAt     -- :: Int -> NonEmpty a -> ([a], [a])
       , takeWhile   -- :: (a -> Bool) -> NonEmpty a -> [a]
       , dropWhile   -- :: (a -> Bool) -> NonEmpty a -> [a]
       , span        -- :: (a -> Bool) -> NonEmpty a -> ([a], [a])
       , break       -- :: (a -> Bool) -> NonEmpty a -> ([a], [a])
       , filter      -- :: (a -> Bool) -> NonEmpty a -> [a]
       , partition   -- :: (a -> Bool) -> NonEmpty a -> ([a],[a])
       , group       -- :: (Foldable f, Eq a) => f a -> [NonEmpty a]
       , groupBy     -- :: Foldable f => (a -> a -> Bool) -> f a -> [NonEmpty a]
       , groupWith     -- :: (Foldable f, Eq b) => (a -> b) -> f a -> [NonEmpty a]
       , groupAllWith  -- :: Ord b => (a -> b) -> [a] -> [NonEmpty a]
       , group1      -- :: Eq a => NonEmpty a -> NonEmpty (NonEmpty a)
       , groupBy1    -- :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
       , groupWith1     -- :: Eq b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
       , groupAllWith1  -- :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
       , permutations   -- :: [a] -> NonEmpty [a]
       , permutations1  -- :: NonEmpty a -> NonEmpty (NonEmpty a)
       -- * Sublist predicates
       , isPrefixOf  -- :: Eq a => [a] -> NonEmpty a -> Bool
       -- * \"Set\" operations
       , nub         -- :: Eq a => NonEmpty a -> NonEmpty a
       , nubBy       -- :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
       -- * Indexing streams
       , (!!)        -- :: NonEmpty a -> Int -> a
       -- * Zipping and unzipping streams
       , zip         -- :: NonEmpty a -> NonEmpty b -> NonEmpty (a,b)
       , zipWith     -- :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c
       , unzip       -- :: Functor f => f (a,b) -> (f a, f b)
       -- * Converting to and from a list
       , fromList    -- :: [a] -> NonEmpty a
       , toList      -- :: NonEmpty a -> [a]
       , nonEmpty    -- :: [a] -> Maybe (NonEmpty a)
       , xor         -- :: NonEmpty Bool -> Bool
       ) where

    import           Prelude             hiding (break, cycle, drop, dropWhile,
                                          filter, foldl, foldr, head, init, iterate,
                                          last, length, map, repeat, reverse,
                                          scanl, scanl1, scanr, scanr1, span,
                                          splitAt, tail, take, takeWhile,
                                          unzip, zip, zipWith, (!!), Applicative(..))
    import qualified Prelude

    import           Control.Applicative (Applicative (..), Alternative (many))
    import           GHC.Internal.Data.Foldable       hiding (length, toList)
    import qualified GHC.Internal.Data.Foldable       as Foldable
    import           GHC.Internal.Data.Function       (on)
    import qualified GHC.Internal.Data.List           as List
    import           GHC.Internal.Data.Ord            (comparing)
    import           GHC.Internal.Base            (NonEmpty(..))
    import           GHC.Internal.Stack.Types     (HasCallStack)

    infixr 5 <|

    -- $setup
    -- >>> import Prelude (negate)

    -- | Number of elements in 'NonEmpty' list.
    length :: NonEmpty a -> Int
    length :: forall a. NonEmpty a -> Int
    length (a
    _ :| [a]
    xs) = Int
    1 Int -> Int -> Int
    forall a. Num a => a -> a -> a
    + [a] -> Int
    forall a. [a] -> Int
    forall (t :: * -> *) a. Foldable t => t a -> Int
    Prelude.length [a]
    xs

    -- | Compute n-ary logic exclusive OR operation on 'NonEmpty' list.
    xor :: NonEmpty Bool -> Bool
    xor :: NonEmpty Bool -> Bool
    xor (Bool
    x :| [Bool]
    xs)   = (Bool -> Bool -> Bool) -> Bool -> [Bool] -> Bool
    forall a b. (a -> b -> b) -> b -> [a] -> b
    forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr Bool -> Bool -> Bool
    xor' Bool
    x [Bool]
    xs
      where xor' :: Bool -> Bool -> Bool
    xor' Bool
    True Bool
    y  = Bool -> Bool
    not Bool
    y
            xor' Bool
    False Bool
    y = Bool
    y

    -- | 'unfold' produces a new stream by repeatedly applying the unfolding
    -- function to the seed value to produce an element of type @b@ and a new
    -- seed value.  When the unfolding function returns 'Nothing' instead of
    -- a new seed value, the stream ends.
    unfold :: (a -> (b, Maybe a)) -> a -> NonEmpty b
    unfold :: forall a b. (a -> (b, Maybe a)) -> a -> NonEmpty b
    unfold a -> (b, Maybe a)
    f a
    a = case a -> (b, Maybe a)
    f a
    a of
      (b
    b, Maybe a
    Nothing) -> b
    b b -> [b] -> NonEmpty b
    forall a. a -> [a] -> NonEmpty a
    :| []
      (b
    b, Just a
    c)  -> b
    b b -> NonEmpty b -> NonEmpty b
    forall a. a -> NonEmpty a -> NonEmpty a
    <| (a -> (b, Maybe a)) -> a -> NonEmpty b
    forall a b. (a -> (b, Maybe a)) -> a -> NonEmpty b
    unfold a -> (b, Maybe a)
    f a
    c
    {-# DEPRECATED unfold "Use unfoldr" #-}
    -- Deprecated in 8.2.1, remove in 8.4

    -- | 'nonEmpty' efficiently turns a normal list into a 'NonEmpty' stream,
    -- producing 'Nothing' if the input is empty.
    nonEmpty :: [a] -> Maybe (NonEmpty a)
    nonEmpty :: forall a. [a] -> Maybe (NonEmpty a)
    nonEmpty []     = Maybe (NonEmpty a)
    forall a. Maybe a
    Nothing
    nonEmpty (a
    a:[a]
    as) = NonEmpty a -> Maybe (NonEmpty a)
    forall a. a -> Maybe a
    Just (a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    as)

    -- | 'uncons' produces the first element of the stream, and a stream of the
    -- remaining elements, if any.
    uncons :: NonEmpty a -> (a, Maybe (NonEmpty a))
    uncons :: forall a. NonEmpty a -> (a, Maybe (NonEmpty a))
    uncons ~(a
    a :| [a]
    as) = (a
    a, [a] -> Maybe (NonEmpty a)
    forall a. [a] -> Maybe (NonEmpty a)
    nonEmpty [a]
    as)

    -- | The 'unfoldr' function is analogous to "Data.List"'s
    -- 'GHC.Internal.Data.List.unfoldr' operation.
    unfoldr :: (a -> (b, Maybe a)) -> a -> NonEmpty b
    unfoldr :: forall a b. (a -> (b, Maybe a)) -> a -> NonEmpty b
    unfoldr a -> (b, Maybe a)
    f a
    a = case a -> (b, Maybe a)
    f a
    a of
      (b
    b, Maybe a
    mc) -> b
    b b -> [b] -> NonEmpty b
    forall a. a -> [a] -> NonEmpty a
    :| [b] -> (a -> [b]) -> Maybe a -> [b]
    forall b a. b -> (a -> b) -> Maybe a -> b
    maybe [] a -> [b]
    go Maybe a
    mc
     where
        go :: a -> [b]
    go a
    c = case a -> (b, Maybe a)
    f a
    c of
          (b
    d, Maybe a
    me) -> b
    d b -> [b] -> [b]
    forall a. a -> [a] -> [a]
    : [b] -> (a -> [b]) -> Maybe a -> [b]
    forall b a. b -> (a -> b) -> Maybe a -> b
    maybe [] a -> [b]
    go Maybe a
    me

    -- | Extract the first element of the stream.
    head :: NonEmpty a -> a
    head :: forall a. NonEmpty a -> a
    head (a
    a :| [a]
    _) = a
    a

    -- | Extract the possibly-empty tail of the stream.
    tail :: NonEmpty a -> [a]
    tail :: forall a. NonEmpty a -> [a]
    tail (a
    _ :| [a]
    as) = [a]
    as

    -- | Extract the last element of the stream.
    last :: NonEmpty a -> a
    last :: forall a. NonEmpty a -> a
    last ~(a
    a :| [a]
    as) = [a] -> a
    forall a. HasCallStack => [a] -> a
    List.last (a
    a a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    : [a]
    as)

    -- | Extract everything except the last element of the stream.
    init :: NonEmpty a -> [a]
    init :: forall a. NonEmpty a -> [a]
    init ~(a
    a :| [a]
    as) = [a] -> [a]
    forall a. HasCallStack => [a] -> [a]
    List.init (a
    a a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    : [a]
    as)

    -- | Construct a 'NonEmpty' list from a single element.
    --
    -- @since 4.15
    singleton :: a -> NonEmpty a
    singleton :: forall a. a -> NonEmpty a
    singleton a
    a = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| []

    -- | Prepend an element to the stream.
    (<|) :: a -> NonEmpty a -> NonEmpty a
    a
    a <| :: forall a. a -> NonEmpty a -> NonEmpty a
    <| ~(a
    b :| [a]
    bs) = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| a
    b a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    : [a]
    bs

    -- | Synonym for '<|'.
    cons :: a -> NonEmpty a -> NonEmpty a
    cons :: forall a. a -> NonEmpty a -> NonEmpty a
    cons = a -> NonEmpty a -> NonEmpty a
    forall a. a -> NonEmpty a -> NonEmpty a
    (<|)

    -- | Sort a stream.
    sort :: Ord a => NonEmpty a -> NonEmpty a
    sort :: forall a. Ord a => NonEmpty a -> NonEmpty a
    sort = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
    forall (f :: * -> *) a b.
    Foldable f =>
    ([a] -> [b]) -> f a -> NonEmpty b
    lift [a] -> [a]
    forall a. Ord a => [a] -> [a]
    List.sort

    -- | Sort a 'NonEmpty' on a user-supplied projection of its elements.
    -- See 'List.sortOn' for more detailed information.
    --
    -- ==== __Examples__
    --
    -- >>> sortOn fst $ (2, "world") :| [(4, "!"), (1, "Hello")]
    -- (1,"Hello") :| [(2,"world"),(4,"!")]
    --
    -- >>> sortOn length $ "jim" :| ["creed", "pam", "michael", "dwight", "kevin"]
    -- "jim" :| ["pam","creed","kevin","dwight","michael"]
    --
    -- ==== __Performance notes__
    --
    -- This function minimises the projections performed, by materialising
    -- the projections in an intermediate list.
    --
    -- For trivial projections, you should prefer using 'sortBy' with
    -- 'comparing', for example:
    --
    -- >>> sortBy (comparing fst) $ (3, 1) :| [(2, 2), (1, 3)]
    -- (1,3) :| [(2,2),(3,1)]
    --
    -- Or, for the exact same API as 'sortOn', you can use `sortBy . comparing`:
    --
    -- >>> (sortBy . comparing) fst $ (3, 1) :| [(2, 2), (1, 3)]
    -- (1,3) :| [(2,2),(3,1)]
    --
    -- 'sortWith' is an alias for `sortBy . comparing`.
    --
    -- @since 4.20.0.0
    sortOn :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
    sortOn :: forall b a. Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
    sortOn a -> b
    f = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
    forall (f :: * -> *) a b.
    Foldable f =>
    ([a] -> [b]) -> f a -> NonEmpty b
    lift ((a -> b) -> [a] -> [a]
    forall b a. Ord b => (a -> b) -> [a] -> [a]
    List.sortOn a -> b
    f)

    -- | Converts a normal list to a 'NonEmpty' stream.
    --
    -- Raises an error if given an empty list.
    fromList :: HasCallStack => [a] -> NonEmpty a
    fromList :: forall a. HasCallStack => [a] -> NonEmpty a
    fromList (a
    a:[a]
    as) = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    as
    fromList [] = [Char] -> NonEmpty a
    forall a. HasCallStack => [Char] -> a
    error [Char]
    "NonEmpty.fromList: empty list"

    -- | Convert a stream to a normal list efficiently.
    toList :: NonEmpty a -> [a]
    toList :: forall a. NonEmpty a -> [a]
    toList ~(a
    a :| [a]
    as) = a
    a a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    : [a]
    as

    -- | Lift list operations to work on a 'NonEmpty' stream.
    --
    -- /Beware/: If the provided function returns an empty list,
    -- this will raise an error.
    lift :: Foldable f => ([a] -> [b]) -> f a -> NonEmpty b
    lift :: forall (f :: * -> *) a b.
    Foldable f =>
    ([a] -> [b]) -> f a -> NonEmpty b
    lift [a] -> [b]
    f = [b] -> NonEmpty b
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([b] -> NonEmpty b) -> (f a -> [b]) -> f a -> NonEmpty b
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [b]
    f ([a] -> [b]) -> (f a -> [a]) -> f a -> [b]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | Map a function over a 'NonEmpty' stream.
    map :: (a -> b) -> NonEmpty a -> NonEmpty b
    map :: forall a b. (a -> b) -> NonEmpty a -> NonEmpty b
    map a -> b
    f ~(a
    a :| [a]
    as) = a -> b
    f a
    a b -> [b] -> NonEmpty b
    forall a. a -> [a] -> NonEmpty a
    :| (a -> b) -> [a] -> [b]
    forall a b. (a -> b) -> [a] -> [b]
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap a -> b
    f [a]
    as

    -- | The 'inits' function takes a stream @xs@ and returns all the
    -- finite prefixes of @xs@, starting with the shortest. The result is
    -- 'NonEmpty' because the result always contains the empty list as the first
    -- element.
    --
    -- > inits [1,2,3] == [] :| [[1], [1,2], [1,2,3]]
    -- > inits [1] == [] :| [[1]]
    -- > inits [] == [] :| []
    inits :: Foldable f => f a -> NonEmpty [a]
    inits :: forall (f :: * -> *) a. Foldable f => f a -> NonEmpty [a]
    inits = [[a]] -> NonEmpty [a]
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([[a]] -> NonEmpty [a]) -> (f a -> [[a]]) -> f a -> NonEmpty [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [[a]]
    forall a. [a] -> [[a]]
    List.inits ([a] -> [[a]]) -> (f a -> [a]) -> f a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | The 'inits1' function takes a 'NonEmpty' stream @xs@ and returns all the
    -- 'NonEmpty' finite prefixes of @xs@, starting with the shortest.
    --
    -- > inits1 (1 :| [2,3]) == (1 :| []) :| [1 :| [2], 1 :| [2,3]]
    -- > inits1 (1 :| []) == (1 :| []) :| []
    --
    -- @since 4.18
    inits1 :: NonEmpty a -> NonEmpty (NonEmpty a)
    inits1 :: forall a. NonEmpty a -> NonEmpty (NonEmpty a)
    inits1 =
      -- fromList is an unsafe function, but this usage should be safe, since:
      -- * `inits xs = [[], ..., init (init xs), init xs, xs]`
      -- * If `xs` is nonempty, it follows that `inits xs` contains at least one nonempty
      --   list, since `last (inits xs) = xs`.
      -- * The only empty element of `inits xs` is the first one (by the definition of `inits`)
      -- * Therefore, if we take all but the first element of `inits xs` i.e.
      --   `tail (inits xs)`, we have a nonempty list of nonempty lists
      [NonEmpty a] -> NonEmpty (NonEmpty a)
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([NonEmpty a] -> NonEmpty (NonEmpty a))
    -> (NonEmpty a -> [NonEmpty a])
    -> NonEmpty a
    -> NonEmpty (NonEmpty a)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . ([a] -> NonEmpty a) -> [[a]] -> [NonEmpty a]
    forall a b. (a -> b) -> [a] -> [b]
    Prelude.map [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([[a]] -> [NonEmpty a])
    -> (NonEmpty a -> [[a]]) -> NonEmpty a -> [NonEmpty a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . Int -> [[a]] -> [[a]]
    forall a. Int -> [a] -> [a]
    List.drop Int
    1 ([[a]] -> [[a]]) -> (NonEmpty a -> [[a]]) -> NonEmpty a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [[a]]
    forall a. [a] -> [[a]]
    List.inits ([a] -> [[a]]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | The 'tails' function takes a stream @xs@ and returns all the
    -- suffixes of @xs@, starting with the longest. The result is 'NonEmpty'
    -- because the result always contains the empty list as the last element.
    --
    -- > tails [1,2,3] == [1,2,3] :| [[2,3], [3], []]
    -- > tails [1] == [1] :| [[]]
    -- > tails [] == [] :| []
    tails   :: Foldable f => f a -> NonEmpty [a]
    tails :: forall (f :: * -> *) a. Foldable f => f a -> NonEmpty [a]
    tails = [[a]] -> NonEmpty [a]
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([[a]] -> NonEmpty [a]) -> (f a -> [[a]]) -> f a -> NonEmpty [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [[a]]
    forall a. [a] -> [[a]]
    List.tails ([a] -> [[a]]) -> (f a -> [a]) -> f a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | The 'tails1' function takes a 'NonEmpty' stream @xs@ and returns all the
    -- non-empty suffixes of @xs@, starting with the longest.
    --
    -- > tails1 (1 :| [2,3]) == (1 :| [2,3]) :| [2 :| [3], 3 :| []]
    -- > tails1 (1 :| []) == (1 :| []) :| []
    --
    -- @since 4.18
    tails1 :: NonEmpty a -> NonEmpty (NonEmpty a)
    tails1 :: forall a. NonEmpty a -> NonEmpty (NonEmpty a)
    tails1 =
      -- fromList is an unsafe function, but this usage should be safe, since:
      -- * `tails xs = [xs, tail xs, tail (tail xs), ..., []]`
      -- * If `xs` is nonempty, it follows that `tails xs` contains at least one nonempty
      --   list, since `head (tails xs) = xs`.
      -- * The only empty element of `tails xs` is the last one (by the definition of `tails`)
      -- * Therefore, if we take all but the last element of `tails xs` i.e.
      --   `init (tails xs)`, we have a nonempty list of nonempty lists
      [NonEmpty a] -> NonEmpty (NonEmpty a)
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([NonEmpty a] -> NonEmpty (NonEmpty a))
    -> (NonEmpty a -> [NonEmpty a])
    -> NonEmpty a
    -> NonEmpty (NonEmpty a)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . ([a] -> NonEmpty a) -> [[a]] -> [NonEmpty a]
    forall a b. (a -> b) -> [a] -> [b]
    Prelude.map [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([[a]] -> [NonEmpty a])
    -> (NonEmpty a -> [[a]]) -> NonEmpty a -> [NonEmpty a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [[a]] -> [[a]]
    forall a. HasCallStack => [a] -> [a]
    List.init ([[a]] -> [[a]]) -> (NonEmpty a -> [[a]]) -> NonEmpty a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [[a]]
    forall a. [a] -> [[a]]
    List.tails ([a] -> [[a]]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | @'insert' x xs@ inserts @x@ into the last position in @xs@ where it
    -- is still less than or equal to the next element. In particular, if the
    -- list is sorted beforehand, the result will also be sorted.
    insert  :: (Foldable f, Ord a) => a -> f a -> NonEmpty a
    insert :: forall (f :: * -> *) a.
    (Foldable f, Ord a) =>
    a -> f a -> NonEmpty a
    insert a
    a = [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([a] -> NonEmpty a) -> (f a -> [a]) -> f a -> NonEmpty a
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . a -> [a] -> [a]
    forall a. Ord a => a -> [a] -> [a]
    List.insert a
    a ([a] -> [a]) -> (f a -> [a]) -> f a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | @'some1' x@ sequences @x@ one or more times.
    some1 :: Alternative f => f a -> f (NonEmpty a)
    some1 :: forall (f :: * -> *) a. Alternative f => f a -> f (NonEmpty a)
    some1 f a
    x = (a -> [a] -> NonEmpty a) -> f a -> f [a] -> f (NonEmpty a)
    forall a b c. (a -> b -> c) -> f a -> f b -> f c
    forall (f :: * -> *) a b c.
    Applicative f =>
    (a -> b -> c) -> f a -> f b -> f c
    liftA2 a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    (:|) f a
    x (f a -> f [a]
    forall a. f a -> f [a]
    forall (f :: * -> *) a. Alternative f => f a -> f [a]
    many f a
    x)

    -- | 'scanl' is similar to 'foldl', but returns a stream of successive
    -- reduced values from the left:
    --
    -- > scanl f z [x1, x2, ...] == z :| [z `f` x1, (z `f` x1) `f` x2, ...]
    --
    -- Note that
    --
    -- > last (scanl f z xs) == foldl f z xs.
    scanl   :: Foldable f => (b -> a -> b) -> b -> f a -> NonEmpty b
    scanl :: forall (f :: * -> *) b a.
    Foldable f =>
    (b -> a -> b) -> b -> f a -> NonEmpty b
    scanl b -> a -> b
    f b
    z = [b] -> NonEmpty b
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([b] -> NonEmpty b) -> (f a -> [b]) -> f a -> NonEmpty b
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (b -> a -> b) -> b -> [a] -> [b]
    forall b a. (b -> a -> b) -> b -> [a] -> [b]
    List.scanl b -> a -> b
    f b
    z ([a] -> [b]) -> (f a -> [a]) -> f a -> [b]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | 'scanr' is the right-to-left dual of 'scanl'.
    -- Note that
    --
    -- > head (scanr f z xs) == foldr f z xs.
    scanr   :: Foldable f => (a -> b -> b) -> b -> f a -> NonEmpty b
    scanr :: forall (f :: * -> *) a b.
    Foldable f =>
    (a -> b -> b) -> b -> f a -> NonEmpty b
    scanr a -> b -> b
    f b
    z = [b] -> NonEmpty b
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([b] -> NonEmpty b) -> (f a -> [b]) -> f a -> NonEmpty b
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (a -> b -> b) -> b -> [a] -> [b]
    forall a b. (a -> b -> b) -> b -> [a] -> [b]
    List.scanr a -> b -> b
    f b
    z ([a] -> [b]) -> (f a -> [a]) -> f a -> [b]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList

    -- | 'scanl1' is a variant of 'scanl' that has no starting value argument:
    --
    -- > scanl1 f [x1, x2, ...] == x1 :| [x1 `f` x2, x1 `f` (x2 `f` x3), ...]
    scanl1 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
    scanl1 :: forall a. (a -> a -> a) -> NonEmpty a -> NonEmpty a
    scanl1 a -> a -> a
    f ~(a
    a :| [a]
    as) = [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ((a -> a -> a) -> a -> [a] -> [a]
    forall b a. (b -> a -> b) -> b -> [a] -> [b]
    List.scanl a -> a -> a
    f a
    a [a]
    as)

    -- | 'scanr1' is a variant of 'scanr' that has no starting value argument.
    scanr1 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
    scanr1 :: forall a. (a -> a -> a) -> NonEmpty a -> NonEmpty a
    scanr1 a -> a -> a
    f ~(a
    a :| [a]
    as) = [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ((a -> a -> a) -> [a] -> [a]
    forall a. (a -> a -> a) -> [a] -> [a]
    List.scanr1 a -> a -> a
    f (a
    aa -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :[a]
    as))

    -- | 'intersperse x xs' alternates elements of the list with copies of @x@.
    --
    -- > intersperse 0 (1 :| [2,3]) == 1 :| [0,2,0,3]
    intersperse :: a -> NonEmpty a -> NonEmpty a
    intersperse :: forall a. a -> NonEmpty a -> NonEmpty a
    intersperse a
    a ~(a
    b :| [a]
    bs) = a
    b a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| case [a]
    bs of
        [] -> []
        [a]
    _ -> a
    a a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    : a -> [a] -> [a]
    forall a. a -> [a] -> [a]
    List.intersperse a
    a [a]
    bs

    -- | @'iterate' f x@ produces the infinite sequence
    -- of repeated applications of @f@ to @x@.
    --
    -- > iterate f x = x :| [f x, f (f x), ..]
    iterate :: (a -> a) -> a -> NonEmpty a
    iterate :: forall a. (a -> a) -> a -> NonEmpty a
    iterate a -> a
    f a
    a = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| (a -> a) -> a -> [a]
    forall a. (a -> a) -> a -> [a]
    List.iterate a -> a
    f (a -> a
    f a
    a)

    -- | @'cycle' xs@ returns the infinite repetition of @xs@:
    --
    -- > cycle (1 :| [2,3]) = 1 :| [2,3,1,2,3,...]
    cycle :: NonEmpty a -> NonEmpty a
    cycle :: forall a. NonEmpty a -> NonEmpty a
    cycle = [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([a] -> NonEmpty a)
    -> (NonEmpty a -> [a]) -> NonEmpty a -> NonEmpty a
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [a] -> [a]
    forall a. HasCallStack => [a] -> [a]
    List.cycle ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | 'reverse' a finite NonEmpty stream.
    reverse :: NonEmpty a -> NonEmpty a
    reverse :: forall a. NonEmpty a -> NonEmpty a
    reverse = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
    forall (f :: * -> *) a b.
    Foldable f =>
    ([a] -> [b]) -> f a -> NonEmpty b
    lift [a] -> [a]
    forall a. [a] -> [a]
    List.reverse

    -- | @'repeat' x@ returns a constant stream, where all elements are
    -- equal to @x@.
    repeat :: a -> NonEmpty a
    repeat :: forall a. a -> NonEmpty a
    repeat a
    a = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| a -> [a]
    forall a. a -> [a]
    List.repeat a
    a

    -- | @'take' n xs@ returns the first @n@ elements of @xs@.
    take :: Int -> NonEmpty a -> [a]
    take :: forall a. Int -> NonEmpty a -> [a]
    take Int
    n = Int -> [a] -> [a]
    forall a. Int -> [a] -> [a]
    List.take Int
    n ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | @'drop' n xs@ drops the first @n@ elements off the front of
    -- the sequence @xs@.
    drop :: Int -> NonEmpty a -> [a]
    drop :: forall a. Int -> NonEmpty a -> [a]
    drop Int
    n = Int -> [a] -> [a]
    forall a. Int -> [a] -> [a]
    List.drop Int
    n ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | @'splitAt' n xs@ returns a pair consisting of the prefix of @xs@
    -- of length @n@ and the remaining stream immediately following this prefix.
    --
    -- > 'splitAt' n xs == ('take' n xs, 'drop' n xs)
    -- > xs == ys ++ zs where (ys, zs) = 'splitAt' n xs
    splitAt :: Int -> NonEmpty a -> ([a],[a])
    splitAt :: forall a. Int -> NonEmpty a -> ([a], [a])
    splitAt Int
    n = Int -> [a] -> ([a], [a])
    forall a. Int -> [a] -> ([a], [a])
    List.splitAt Int
    n ([a] -> ([a], [a]))
    -> (NonEmpty a -> [a]) -> NonEmpty a -> ([a], [a])
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | @'takeWhile' p xs@ returns the longest prefix of the stream
    -- @xs@ for which the predicate @p@ holds.
    takeWhile :: (a -> Bool) -> NonEmpty a -> [a]
    takeWhile :: forall a. (a -> Bool) -> NonEmpty a -> [a]
    takeWhile a -> Bool
    p = (a -> Bool) -> [a] -> [a]
    forall a. (a -> Bool) -> [a] -> [a]
    List.takeWhile a -> Bool
    p ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | @'dropWhile' p xs@ returns the suffix remaining after
    -- @'takeWhile' p xs@.
    dropWhile :: (a -> Bool) -> NonEmpty a -> [a]
    dropWhile :: forall a. (a -> Bool) -> NonEmpty a -> [a]
    dropWhile a -> Bool
    p = (a -> Bool) -> [a] -> [a]
    forall a. (a -> Bool) -> [a] -> [a]
    List.dropWhile a -> Bool
    p ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | @'span' p xs@ returns the longest prefix of @xs@ that satisfies
    -- @p@, together with the remainder of the stream.
    --
    -- > 'span' p xs == ('takeWhile' p xs, 'dropWhile' p xs)
    -- > xs == ys ++ zs where (ys, zs) = 'span' p xs
    span :: (a -> Bool) -> NonEmpty a -> ([a], [a])
    span :: forall a. (a -> Bool) -> NonEmpty a -> ([a], [a])
    span a -> Bool
    p = (a -> Bool) -> [a] -> ([a], [a])
    forall a. (a -> Bool) -> [a] -> ([a], [a])
    List.span a -> Bool
    p ([a] -> ([a], [a]))
    -> (NonEmpty a -> [a]) -> NonEmpty a -> ([a], [a])
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | The @'break' p@ function is equivalent to @'span' (not . p)@.
    break :: (a -> Bool) -> NonEmpty a -> ([a], [a])
    break :: forall a. (a -> Bool) -> NonEmpty a -> ([a], [a])
    break a -> Bool
    p = (a -> Bool) -> NonEmpty a -> ([a], [a])
    forall a. (a -> Bool) -> NonEmpty a -> ([a], [a])
    span (Bool -> Bool
    not (Bool -> Bool) -> (a -> Bool) -> a -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . a -> Bool
    p)

    -- | @'filter' p xs@ removes any elements from @xs@ that do not satisfy @p@.
    filter :: (a -> Bool) -> NonEmpty a -> [a]
    filter :: forall a. (a -> Bool) -> NonEmpty a -> [a]
    filter a -> Bool
    p = (a -> Bool) -> [a] -> [a]
    forall a. (a -> Bool) -> [a] -> [a]
    List.filter a -> Bool
    p ([a] -> [a]) -> (NonEmpty a -> [a]) -> NonEmpty a -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | The 'partition' function takes a predicate @p@ and a stream
    -- @xs@, and returns a pair of lists. The first list corresponds to the
    -- elements of @xs@ for which @p@ holds; the second corresponds to the
    -- elements of @xs@ for which @p@ does not hold.
    --
    -- > 'partition' p xs = ('filter' p xs, 'filter' (not . p) xs)
    partition :: (a -> Bool) -> NonEmpty a -> ([a], [a])
    partition :: forall a. (a -> Bool) -> NonEmpty a -> ([a], [a])
    partition a -> Bool
    p = (a -> Bool) -> [a] -> ([a], [a])
    forall a. (a -> Bool) -> [a] -> ([a], [a])
    List.partition a -> Bool
    p ([a] -> ([a], [a]))
    -> (NonEmpty a -> [a]) -> NonEmpty a -> ([a], [a])
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | The 'group' function takes a stream and returns a list of
    -- streams such that flattening the resulting list is equal to the
    -- argument.  Moreover, each stream in the resulting list
    -- contains only equal elements, and consecutive equal elements
    -- of the input end up in the same stream of the output list.
    -- For example, in list notation:
    --
    -- >>> group "Mississippi"
    -- ["M", "i", "ss", "i", "ss", "i", "pp", "i"]
    group :: (Foldable f, Eq a) => f a -> [NonEmpty a]
    group :: forall (f :: * -> *) a. (Foldable f, Eq a) => f a -> [NonEmpty a]
    group = (a -> a -> Bool) -> f a -> [NonEmpty a]
    forall (f :: * -> *) a.
    Foldable f =>
    (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy a -> a -> Bool
    forall a. Eq a => a -> a -> Bool
    (==)

    -- | 'groupBy' operates like 'group', but uses the provided equality
    -- predicate instead of `==`.
    groupBy :: Foldable f => (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy :: forall (f :: * -> *) a.
    Foldable f =>
    (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy a -> a -> Bool
    eq0 = (a -> a -> Bool) -> [a] -> [NonEmpty a]
    forall {a}. (a -> a -> Bool) -> [a] -> [NonEmpty a]
    go a -> a -> Bool
    eq0 ([a] -> [NonEmpty a]) -> (f a -> [a]) -> f a -> [NonEmpty a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . f a -> [a]
    forall a. f a -> [a]
    forall (t :: * -> *) a. Foldable t => t a -> [a]
    Foldable.toList
      where
        go :: (a -> a -> Bool) -> [a] -> [NonEmpty a]
    go a -> a -> Bool
    _  [] = []
        go a -> a -> Bool
    eq (a
    x : [a]
    xs) = (a
    x a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    ys) NonEmpty a -> [NonEmpty a] -> [NonEmpty a]
    forall a. a -> [a] -> [a]
    : (a -> a -> Bool) -> [a] -> [NonEmpty a]
    forall (f :: * -> *) a.
    Foldable f =>
    (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy a -> a -> Bool
    eq [a]
    zs
          where ([a]
    ys, [a]
    zs) = (a -> Bool) -> [a] -> ([a], [a])
    forall a. (a -> Bool) -> [a] -> ([a], [a])
    List.span (a -> a -> Bool
    eq a
    x) [a]
    xs

    -- | 'groupWith' operates like 'group', but uses the provided projection when
    -- comparing for equality
    groupWith :: (Foldable f, Eq b) => (a -> b) -> f a -> [NonEmpty a]
    groupWith :: forall (f :: * -> *) b a.
    (Foldable f, Eq b) =>
    (a -> b) -> f a -> [NonEmpty a]
    groupWith a -> b
    f = (a -> a -> Bool) -> f a -> [NonEmpty a]
    forall (f :: * -> *) a.
    Foldable f =>
    (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy (b -> b -> Bool
    forall a. Eq a => a -> a -> Bool
    (==) (b -> b -> Bool) -> (a -> b) -> a -> a -> Bool
    forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
    `on` a -> b
    f)

    -- | 'groupAllWith' operates like 'groupWith', but sorts the list
    -- first so that each equivalence class has, at most, one list in the
    -- output
    groupAllWith :: (Ord b) => (a -> b) -> [a] -> [NonEmpty a]
    groupAllWith :: forall b a. Ord b => (a -> b) -> [a] -> [NonEmpty a]
    groupAllWith a -> b
    f = (a -> b) -> [a] -> [NonEmpty a]
    forall (f :: * -> *) b a.
    (Foldable f, Eq b) =>
    (a -> b) -> f a -> [NonEmpty a]
    groupWith a -> b
    f ([a] -> [NonEmpty a]) -> ([a] -> [a]) -> [a] -> [NonEmpty a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (a -> a -> Ordering) -> [a] -> [a]
    forall a. (a -> a -> Ordering) -> [a] -> [a]
    List.sortBy (b -> b -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare (b -> b -> Ordering) -> (a -> b) -> a -> a -> Ordering
    forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
    `on` a -> b
    f)

    -- | 'group1' operates like 'group', but uses the knowledge that its
    -- input is non-empty to produce guaranteed non-empty output.
    group1 :: Eq a => NonEmpty a -> NonEmpty (NonEmpty a)
    group1 :: forall a. Eq a => NonEmpty a -> NonEmpty (NonEmpty a)
    group1 = (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    forall a. (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupBy1 a -> a -> Bool
    forall a. Eq a => a -> a -> Bool
    (==)

    -- | 'groupBy1' is to 'group1' as 'groupBy' is to 'group'.
    groupBy1 :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupBy1 :: forall a. (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupBy1 a -> a -> Bool
    eq (a
    x :| [a]
    xs) = (a
    x a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    ys) NonEmpty a -> [NonEmpty a] -> NonEmpty (NonEmpty a)
    forall a. a -> [a] -> NonEmpty a
    :| (a -> a -> Bool) -> [a] -> [NonEmpty a]
    forall (f :: * -> *) a.
    Foldable f =>
    (a -> a -> Bool) -> f a -> [NonEmpty a]
    groupBy a -> a -> Bool
    eq [a]
    zs
      where ([a]
    ys, [a]
    zs) = (a -> Bool) -> [a] -> ([a], [a])
    forall a. (a -> Bool) -> [a] -> ([a], [a])
    List.span (a -> a -> Bool
    eq a
    x) [a]
    xs

    -- | 'groupWith1' is to 'group1' as 'groupWith' is to 'group'
    groupWith1 :: (Eq b) => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupWith1 :: forall b a. Eq b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupWith1 a -> b
    f = (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    forall a. (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupBy1 (b -> b -> Bool
    forall a. Eq a => a -> a -> Bool
    (==) (b -> b -> Bool) -> (a -> b) -> a -> a -> Bool
    forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
    `on` a -> b
    f)

    -- | 'groupAllWith1' is to 'groupWith1' as 'groupAllWith' is to 'groupWith'
    groupAllWith1 :: (Ord b) => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupAllWith1 :: forall b a.
    Ord b =>
    (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupAllWith1 a -> b
    f = (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    forall b a. Eq b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a)
    groupWith1 a -> b
    f (NonEmpty a -> NonEmpty (NonEmpty a))
    -> (NonEmpty a -> NonEmpty a)
    -> NonEmpty a
    -> NonEmpty (NonEmpty a)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (a -> b) -> NonEmpty a -> NonEmpty a
    forall b a. Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
    sortWith a -> b
    f

    -- | The 'permutations' function returns the list of all permutations of the argument.
    --
    -- @since 4.20.0.0
    permutations            :: [a] -> NonEmpty [a]
    permutations :: forall a. [a] -> NonEmpty [a]
    permutations [a]
    xs0        =  [a]
    xs0 [a] -> [[a]] -> NonEmpty [a]
    forall a. a -> [a] -> NonEmpty a
    :| [a] -> [a] -> [[a]]
    forall {a}. [a] -> [a] -> [[a]]
    perms [a]
    xs0 []
      where
        perms :: [a] -> [a] -> [[a]]
    perms []     [a]
    _  = []
        perms (a
    t:[a]
    ts) [a]
    is = ([a] -> [[a]] -> [[a]]) -> [[a]] -> NonEmpty [a] -> [[a]]
    forall a b. (a -> b -> b) -> b -> NonEmpty a -> b
    forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr [a] -> [[a]] -> [[a]]
    interleave ([a] -> [a] -> [[a]]
    perms [a]
    ts (a
    ta -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :[a]
    is)) ([a] -> NonEmpty [a]
    forall a. [a] -> NonEmpty [a]
    permutations [a]
    is)
          where interleave :: [a] -> [[a]] -> [[a]]
    interleave    [a]
    xs     [[a]]
    r = let ([a]
    _,[[a]]
    zs) = ([a] -> [a]) -> [a] -> [[a]] -> ([a], [[a]])
    interleave' [a] -> [a]
    forall a. a -> a
    id [a]
    xs [[a]]
    r in [[a]]
    zs
                interleave' :: ([a] -> [a]) -> [a] -> [[a]] -> ([a], [[a]])
    interleave' [a] -> [a]
    _ []     [[a]]
    r = ([a]
    ts, [[a]]
    r)
                interleave' [a] -> [a]
    f (a
    y:[a]
    ys) [[a]]
    r = let ([a]
    us,[[a]]
    zs) = ([a] -> [a]) -> [a] -> [[a]] -> ([a], [[a]])
    interleave' ([a] -> [a]
    f ([a] -> [a]) -> ([a] -> [a]) -> [a] -> [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (a
    ya -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :)) [a]
    ys [[a]]
    r
                                         in  (a
    ya -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :[a]
    us, [a] -> [a]
    f (a
    ta -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :a
    ya -> [a] -> [a]
    forall a. a -> [a] -> [a]
    :[a]
    us) [a] -> [[a]] -> [[a]]
    forall a. a -> [a] -> [a]
    : [[a]]
    zs)
    -- The implementation of 'permutations' is adopted from 'GHC.Internal.Data.List.permutations',
    -- see there for discussion and explanations.

    -- | 'permutations1' operates like 'permutations', but uses the knowledge that its input is
    -- non-empty to produce output where every element is non-empty.
    --
    -- > permutations1 = fmap fromList . permutations . toList
    --
    -- @since 4.20.0.0
    permutations1 :: NonEmpty a -> NonEmpty (NonEmpty a)
    permutations1 :: forall a. NonEmpty a -> NonEmpty (NonEmpty a)
    permutations1 NonEmpty a
    xs = [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([a] -> NonEmpty a) -> NonEmpty [a] -> NonEmpty (NonEmpty a)
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> [a] -> NonEmpty [a]
    forall a. [a] -> NonEmpty [a]
    permutations (NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList NonEmpty a
    xs)

    -- | The 'isPrefixOf' function returns 'True' if the first argument is
    -- a prefix of the second.
    isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool
    isPrefixOf :: forall a. Eq a => [a] -> NonEmpty a -> Bool
    isPrefixOf [] NonEmpty a
    _ = Bool
    True
    isPrefixOf (a
    y:[a]
    ys) (a
    x :| [a]
    xs) = (a
    y a -> a -> Bool
    forall a. Eq a => a -> a -> Bool
    == a
    x) Bool -> Bool -> Bool
    && [a] -> [a] -> Bool
    forall a. Eq a => [a] -> [a] -> Bool
    List.isPrefixOf [a]
    ys [a]
    xs

    -- | @xs !! n@ returns the element of the stream @xs@ at index
    -- @n@. Note that the head of the stream has index 0.
    --
    -- /Beware/: a negative or out-of-bounds index will cause an error.
    (!!) :: HasCallStack => NonEmpty a -> Int -> a
    !! :: forall a. HasCallStack => NonEmpty a -> Int -> a
    (!!) ~(a
    x :| [a]
    xs) Int
    n
      | Int
    n Int -> Int -> Bool
    forall a. Eq a => a -> a -> Bool
    == Int
    0 = a
    x
      | Int
    n Int -> Int -> Bool
    forall a. Ord a => a -> a -> Bool
    > Int
    0  = [a]
    xs [a] -> Int -> a
    forall a. HasCallStack => [a] -> Int -> a
    List.!! (Int
    n Int -> Int -> Int
    forall a. Num a => a -> a -> a
    - Int
    1)
      | Bool
    otherwise = [Char] -> a
    forall a. HasCallStack => [Char] -> a
    error [Char]
    "NonEmpty.!! negative index"
    infixl 9 !!

    -- | The 'zip' function takes two streams and returns a stream of
    -- corresponding pairs.
    zip :: NonEmpty a -> NonEmpty b -> NonEmpty (a,b)
    zip :: forall a b. NonEmpty a -> NonEmpty b -> NonEmpty (a, b)
    zip ~(a
    x :| [a]
    xs) ~(b
    y :| [b]
    ys) = (a
    x, b
    y) (a, b) -> [(a, b)] -> NonEmpty (a, b)
    forall a. a -> [a] -> NonEmpty a
    :| [a] -> [b] -> [(a, b)]
    forall a b. [a] -> [b] -> [(a, b)]
    List.zip [a]
    xs [b]
    ys

    -- | The 'zipWith' function generalizes 'zip'. Rather than tupling
    -- the elements, the elements are combined using the function
    -- passed as the first argument.
    zipWith :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c
    zipWith :: forall a b c.
    (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c
    zipWith a -> b -> c
    f ~(a
    x :| [a]
    xs) ~(b
    y :| [b]
    ys) = a -> b -> c
    f a
    x b
    y c -> [c] -> NonEmpty c
    forall a. a -> [a] -> NonEmpty a
    :| (a -> b -> c) -> [a] -> [b] -> [c]
    forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
    List.zipWith a -> b -> c
    f [a]
    xs [b]
    ys

    -- | The 'unzip' function is the inverse of the 'zip' function.
    unzip :: Functor f => f (a,b) -> (f a, f b)
    unzip :: forall (f :: * -> *) a b. Functor f => f (a, b) -> (f a, f b)
    unzip f (a, b)
    xs = ((a, b) -> a
    forall a b. (a, b) -> a
    fst ((a, b) -> a) -> f (a, b) -> f a
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> f (a, b)
    xs, (a, b) -> b
    forall a b. (a, b) -> b
    snd ((a, b) -> b) -> f (a, b) -> f b
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> f (a, b)
    xs)
    {-# WARNING in "x-data-list-nonempty-unzip" unzip "This function will be made monomorphic in base-4.22, consider switching to Data.Functor.unzip" #-}

    -- | The 'nub' function removes duplicate elements from a list. In
    -- particular, it keeps only the first occurrence of each element.
    -- (The name 'nub' means \'essence\'.)
    -- It is a special case of 'nubBy', which allows the programmer to
    -- supply their own inequality test.
    nub :: Eq a => NonEmpty a -> NonEmpty a
    nub :: forall a. Eq a => NonEmpty a -> NonEmpty a
    nub = (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
    forall a. (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
    nubBy a -> a -> Bool
    forall a. Eq a => a -> a -> Bool
    (==)

    -- | The 'nubBy' function behaves just like 'nub', except it uses a
    -- user-supplied equality predicate instead of the overloaded '=='
    -- function.
    nubBy :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
    nubBy :: forall a. (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
    nubBy a -> a -> Bool
    eq (a
    a :| [a]
    as) = a
    a a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| (a -> a -> Bool) -> [a] -> [a]
    forall a. (a -> a -> Bool) -> [a] -> [a]
    List.nubBy a -> a -> Bool
    eq ((a -> Bool) -> [a] -> [a]
    forall a. (a -> Bool) -> [a] -> [a]
    List.filter (\a
    b -> Bool -> Bool
    not (a -> a -> Bool
    eq a
    a a
    b)) [a]
    as)

    -- | 'transpose' for 'NonEmpty', behaves the same as 'GHC.Internal.Data.List.transpose'
    -- The rows/columns need not be the same length, in which case
    -- > transpose . transpose /= id
    transpose :: NonEmpty (NonEmpty a) -> NonEmpty (NonEmpty a)
    transpose :: forall a. NonEmpty (NonEmpty a) -> NonEmpty (NonEmpty a)
    transpose = ([a] -> NonEmpty a) -> NonEmpty [a] -> NonEmpty (NonEmpty a)
    forall a b. (a -> b) -> NonEmpty a -> NonEmpty b
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap [a] -> NonEmpty a
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList
              (NonEmpty [a] -> NonEmpty (NonEmpty a))
    -> (NonEmpty (NonEmpty a) -> NonEmpty [a])
    -> NonEmpty (NonEmpty a)
    -> NonEmpty (NonEmpty a)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [[a]] -> NonEmpty [a]
    forall a. HasCallStack => [a] -> NonEmpty a
    fromList ([[a]] -> NonEmpty [a])
    -> (NonEmpty (NonEmpty a) -> [[a]])
    -> NonEmpty (NonEmpty a)
    -> NonEmpty [a]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [[a]] -> [[a]]
    forall a. [[a]] -> [[a]]
    List.transpose ([[a]] -> [[a]])
    -> (NonEmpty (NonEmpty a) -> [[a]])
    -> NonEmpty (NonEmpty a)
    -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . NonEmpty [a] -> [[a]]
    forall a. NonEmpty a -> [a]
    toList
              (NonEmpty [a] -> [[a]])
    -> (NonEmpty (NonEmpty a) -> NonEmpty [a])
    -> NonEmpty (NonEmpty a)
    -> [[a]]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (NonEmpty a -> [a]) -> NonEmpty (NonEmpty a) -> NonEmpty [a]
    forall a b. (a -> b) -> NonEmpty a -> NonEmpty b
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList

    -- | 'sortBy' for 'NonEmpty', behaves the same as 'GHC.Internal.Data.List.sortBy'
    sortBy :: (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
    sortBy :: forall a. (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
    sortBy a -> a -> Ordering
    f = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
    forall (f :: * -> *) a b.
    Foldable f =>
    ([a] -> [b]) -> f a -> NonEmpty b
    lift ((a -> a -> Ordering) -> [a] -> [a]
    forall a. (a -> a -> Ordering) -> [a] -> [a]
    List.sortBy a -> a -> Ordering
    f)

    -- | 'sortWith' for 'NonEmpty', behaves the same as:
    --
    -- > sortBy . comparing
    sortWith :: Ord o => (a -> o) -> NonEmpty a -> NonEmpty a
    sortWith :: forall b a. Ord b => (a -> b) -> NonEmpty a -> NonEmpty a
    sortWith = (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
    forall a. (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
    sortBy ((a -> a -> Ordering) -> NonEmpty a -> NonEmpty a)
    -> ((a -> o) -> a -> a -> Ordering)
    -> (a -> o)
    -> NonEmpty a
    -> NonEmpty a
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (a -> o) -> a -> a -> Ordering
    forall a b. Ord a => (b -> a) -> b -> b -> Ordering
    comparing

    -- | A monomorphic version of '<>' for 'NonEmpty'.
    --
    -- >>> append (1 :| []) (2 :| [3])
    -- 1 :| [2,3]
    --
    -- @since 4.16
    append :: NonEmpty a -> NonEmpty a -> NonEmpty a
    append :: forall a. NonEmpty a -> NonEmpty a -> NonEmpty a
    append = NonEmpty a -> NonEmpty a -> NonEmpty a
    forall a. Semigroup a => a -> a -> a
    (<>)

    -- | Attach a list at the end of a 'NonEmpty'.
    --
    -- >>> appendList (1 :| [2,3]) []
    -- 1 :| [2,3]
    --
    -- >>> appendList (1 :| [2,3]) [4,5]
    -- 1 :| [2,3,4,5]
    --
    -- @since 4.16
    appendList :: NonEmpty a -> [a] -> NonEmpty a
    appendList :: forall a. NonEmpty a -> [a] -> NonEmpty a
    appendList (a
    x :| [a]
    xs) [a]
    ys = a
    x a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    xs [a] -> [a] -> [a]
    forall a. Semigroup a => a -> a -> a
    <> [a]
    ys

    -- | Attach a list at the beginning of a 'NonEmpty'.
    --
    -- >>> prependList [] (1 :| [2,3])
    -- 1 :| [2,3]
    --
    -- >>> prependList [negate 1, 0] (1 :| [2, 3])
    -- -1 :| [0,1,2,3]
    --
    -- @since 4.16
    prependList :: [a] -> NonEmpty a -> NonEmpty a
    prependList :: forall a. [a] -> NonEmpty a -> NonEmpty a
    prependList [a]
    ls NonEmpty a
    ne = case [a]
    ls of
      [] -> NonEmpty a
    ne
      (a
    x : [a]
    xs) -> a
    x a -> [a] -> NonEmpty a
    forall a. a -> [a] -> NonEmpty a
    :| [a]
    xs [a] -> [a] -> [a]
    forall a. Semigroup a => a -> a -> a
    <> NonEmpty a -> [a]
    forall a. NonEmpty a -> [a]
    toList NonEmpty a
    ne