{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# 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        -- :: NonEmpty a -> NonEmpty a
   , reverse     -- :: NonEmpty a -> NonEmpty a
   , inits       -- :: Foldable f => f a -> NonEmpty a
   , tails       -- :: Foldable f => f 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   -- :: Int -> NonEmpty a -> [a]
   , dropWhile   -- :: Int -> NonEmpty a -> [a]
   , span        -- :: Int -> NonEmpty a -> ([a],[a])
   , break       -- :: Int -> 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  -- :: (Foldable f, Ord b) => (a -> b) -> f a -> [NonEmpty a]
   , group1      -- :: Eq a => NonEmpty a -> NonEmpty (NonEmpty a)
   , groupBy1    -- :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
   , groupWith1     -- :: (Foldable f, Eq b) => (a -> b) -> f a -> NonEmpty (NonEmpty a)
   , groupAllWith1  -- :: (Foldable f, Ord b) => (a -> b) -> f a -> NonEmpty (NonEmpty a)
   -- * Sublist predicates
   , isPrefixOf  -- :: Foldable f => f 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       -- :: NonEmpty (a, b) -> (NonEmpty a, NonEmpty b)
   -- * Converting to and from a list
   , fromList    -- :: [a] -> NonEmpty a
   , toList      -- :: NonEmpty a -> [a]
   , nonEmpty    -- :: [a] -> Maybe (NonEmpty a)
   , xor         -- :: NonEmpty a -> 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, (!!))
import qualified Prelude

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

infixr 5 <|

-- | Number of elements in 'NonEmpty' list.
length :: NonEmpty a -> Int
length :: NonEmpty a -> Int
length (a
_ :| [a]
xs) = Int
1 Int -> Int -> Int
forall a. Num a => a -> a -> a
External instance of the constraint type Num Int
+ [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
External instance of the constraint type Foldable []
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 (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
External instance of the constraint type Foldable []
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 :: (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 :: [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 :: 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
-- 'Data.List.unfoldr' operation.
unfoldr :: (a -> (b, Maybe a)) -> a -> NonEmpty b
unfoldr :: (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 :: NonEmpty a -> a
head ~(a
a :| [a]
_) = a
a

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

-- | Extract the last element of the stream.
last :: NonEmpty a -> a
last :: NonEmpty a -> a
last ~(a
a :| [a]
as) = [a] -> a
forall a. [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 :: NonEmpty a -> [a]
init ~(a
a :| [a]
as) = [a] -> [a]
forall a. [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 :: 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 <| :: 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 :: 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 :: NonEmpty a -> NonEmpty a
sort = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
forall (f :: * -> *) a b.
Foldable f =>
([a] -> [b]) -> f a -> NonEmpty b
External instance of the constraint type Foldable NonEmpty
lift [a] -> [a]
forall a. Ord a => [a] -> [a]
Evidence bound by a type signature of the constraint type Ord a
List.sort

-- | Converts a normal list to a 'NonEmpty' stream.
--
-- Raises an error if given an empty list.
fromList :: [a] -> NonEmpty a
fromList :: [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. [Char] -> a
errorWithoutStackTrace [Char]
"NonEmpty.fromList: empty list"

-- | Convert a stream to a normal list efficiently.
toList :: NonEmpty a -> [a]
toList :: 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 :: ([a] -> [b]) -> f a -> NonEmpty b
lift [a] -> [b]
f = [b] -> NonEmpty b
forall a. [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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
Foldable.toList

-- | Map a function over a 'NonEmpty' stream.
map :: (a -> b) -> NonEmpty a -> NonEmpty b
map :: (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 (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type Functor []
fmap a -> b
f [a]
as

-- | The 'inits' function takes a stream @xs@ and returns all the
-- finite prefixes of @xs@.
inits :: Foldable f => f a -> NonEmpty [a]
inits :: f a -> NonEmpty [a]
inits = [[a]] -> NonEmpty [a]
forall a. [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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
Foldable.toList

-- | The 'tails' function takes a stream @xs@ and returns all the
-- suffixes of @xs@.
tails   :: Foldable f => f a -> NonEmpty [a]
tails :: f a -> NonEmpty [a]
tails = [[a]] -> NonEmpty [a]
forall a. [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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
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 :: a -> f a -> NonEmpty a
insert a
a = [a] -> NonEmpty a
forall a. [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]
Evidence bound by a type signature of the constraint type Ord 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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
Foldable.toList

-- | @'some1' x@ sequences @x@ one or more times.
some1 :: Alternative f => f a -> f (NonEmpty a)
some1 :: f a -> f (NonEmpty a)
some1 f a
x = (a -> [a] -> NonEmpty a) -> f a -> f [a] -> f (NonEmpty a)
forall (f :: * -> *) a b c.
Applicative f =>
(a -> b -> c) -> f a -> f b -> f c
External instance of the constraint type forall (f :: * -> *). Alternative f => Applicative f
Evidence bound by a type signature of the constraint type Alternative f
liftA2 a -> [a] -> NonEmpty a
forall a. a -> [a] -> NonEmpty a
(:|) f a
x (f a -> f [a]
forall (f :: * -> *) a. Alternative f => f a -> f [a]
Evidence bound by a type signature of the constraint type Alternative f
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 :: (b -> a -> b) -> b -> f a -> NonEmpty b
scanl b -> a -> b
f b
z = [b] -> NonEmpty b
forall a. [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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
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 :: (a -> b -> b) -> b -> f a -> NonEmpty b
scanr a -> b -> b
f b
z = [b] -> NonEmpty b
forall a. [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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
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 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
scanl1 a -> a -> a
f ~(a
a :| [a]
as) = [a] -> NonEmpty a
forall a. [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 :: (a -> a -> a) -> NonEmpty a -> NonEmpty a
scanr1 a -> a -> a
f ~(a
a :| [a]
as) = [a] -> NonEmpty a
forall a. [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 :: 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 :: (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 :: NonEmpty a -> NonEmpty a
cycle = [a] -> NonEmpty a
forall a. [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. [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 :: NonEmpty a -> NonEmpty a
reverse = ([a] -> [a]) -> NonEmpty a -> NonEmpty a
forall (f :: * -> *) a b.
Foldable f =>
([a] -> [b]) -> f a -> NonEmpty b
External instance of the constraint type Foldable NonEmpty
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 :: 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 :: 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 :: 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 :: 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 :: (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 :: (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 :: (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 :: (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 :: (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 :: (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.  For example, in list notation:
--
-- > 'group' $ 'cycle' "Mississippi"
-- >   = "M" : "i" : "ss" : "i" : "ss" : "i" : "pp" : "i" : "M" : "i" : ...
group :: (Foldable f, Eq a) => f a -> [NonEmpty a]
group :: f a -> [NonEmpty a]
group = (a -> a -> Bool) -> f a -> [NonEmpty a]
forall (f :: * -> *) a.
Foldable f =>
(a -> a -> Bool) -> f a -> [NonEmpty a]
Evidence bound by a type signature of the constraint type Foldable f
groupBy a -> a -> Bool
forall a. Eq a => a -> a -> Bool
Evidence bound by a type signature of the constraint type Eq a
(==)

-- | 'groupBy' operates like 'group', but uses the provided equality
-- predicate instead of `==`.
groupBy :: Foldable f => (a -> a -> Bool) -> f a -> [NonEmpty a]
groupBy :: (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 (t :: * -> *) a. Foldable t => t a -> [a]
Evidence bound by a type signature of the constraint type Foldable f
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]
External instance of the constraint type Foldable []
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 :: (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]
Evidence bound by a type signature of the constraint type Foldable f
groupBy (b -> b -> Bool
forall a. Eq a => a -> a -> Bool
Evidence bound by a type signature of the constraint type Eq b
(==) (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 :: (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]
External instance of the constraint type forall a. Ord a => Eq a
Evidence bound by a type signature of the constraint type Ord b
External instance of the constraint type Foldable []
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
Evidence bound by a type signature of the constraint type Ord b
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 :: 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
Evidence bound by a type signature of the constraint type Eq a
(==)

-- | 'groupBy1' is to 'group1' as 'groupBy' is to 'group'.
groupBy1 :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty (NonEmpty a)
groupBy1 :: (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]
External instance of the constraint type Foldable []
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 :: (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
Evidence bound by a type signature of the constraint type Eq b
(==) (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 :: (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)
External instance of the constraint type forall a. Ord a => Eq a
Evidence bound by a type signature of the constraint type Ord b
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 o a. Ord o => (a -> o) -> NonEmpty a -> NonEmpty a
Evidence bound by a type signature of the constraint type Ord b
sortWith a -> b
f

-- | The 'isPrefixOf' function returns 'True' if the first argument is
-- a prefix of the second.
isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool
isPrefixOf :: [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
Evidence bound by a type signature of the constraint type Eq a
== a
x) Bool -> Bool -> Bool
&& [a] -> [a] -> Bool
forall a. Eq a => [a] -> [a] -> Bool
Evidence bound by a type signature of the constraint type Eq a
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.
(!!) :: NonEmpty a -> Int -> a
!! :: NonEmpty a -> Int -> a
(!!) ~(a
x :| [a]
xs) Int
n
  | Int
n Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq Int
== Int
0 = a
x
  | Int
n Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
External instance of the constraint type Ord Int
> Int
0  = [a]
xs [a] -> Int -> a
forall a. [a] -> Int -> a
List.!! (Int
n Int -> Int -> Int
forall a. Num a => a -> a -> a
External instance of the constraint type Num Int
- Int
1)
  | Bool
otherwise = [Char] -> a
forall a. [Char] -> a
errorWithoutStackTrace [Char]
"NonEmpty.!! negative argument"
infixl 9 !!

-- | The 'zip' function takes two streams and returns a stream of
-- corresponding pairs.
zip :: NonEmpty a -> NonEmpty b -> NonEmpty (a,b)
zip :: 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 :: (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 :: 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
Evidence bound by a type signature of the constraint type Functor f
<$> f (a, b)
xs, (a, b) -> b
forall a b. (a, b) -> b
snd ((a, b) -> b) -> f (a, b) -> f b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
Evidence bound by a type signature of the constraint type Functor f
<$> f (a, b)
xs)

-- | 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 :: 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
Evidence bound by a type signature of the constraint type Eq a
(==)

-- | 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 :: (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 '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 :: NonEmpty (NonEmpty a) -> NonEmpty (NonEmpty a)
transpose = ([a] -> NonEmpty a) -> NonEmpty [a] -> NonEmpty (NonEmpty a)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type Functor NonEmpty
fmap [a] -> NonEmpty a
forall a. [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. [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 (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type Functor NonEmpty
fmap NonEmpty a -> [a]
forall a. NonEmpty a -> [a]
toList

-- | 'sortBy' for 'NonEmpty', behaves the same as 'Data.List.sortBy'
sortBy :: (a -> a -> Ordering) -> NonEmpty a -> NonEmpty a
sortBy :: (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
External instance of the constraint type Foldable NonEmpty
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 :: (a -> o) -> 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
Evidence bound by a type signature of the constraint type Ord o
comparing