| 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 |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Data.List.NonEmpty
Description
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: base-4.9.0.0
Synopsis
- data NonEmpty a = a :| [a]
- 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
- length :: NonEmpty a -> Int
- head :: NonEmpty a -> a
- tail :: NonEmpty a -> [a]
- last :: NonEmpty a -> a
- init :: NonEmpty a -> [a]
- singleton :: a -> NonEmpty a
- (<|) :: a -> NonEmpty 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
- reverse :: NonEmpty a -> NonEmpty a
- inits :: Foldable f => f a -> NonEmpty [a]
- tails :: Foldable f => f a -> NonEmpty [a]
- append :: NonEmpty a -> NonEmpty a -> NonEmpty a
- appendList :: NonEmpty a -> [a] -> NonEmpty a
- prependList :: [a] -> NonEmpty a -> NonEmpty a
- 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)
- 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)
- isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool
- nub :: Eq a => NonEmpty a -> NonEmpty a
- nubBy :: (a -> a -> Bool) -> NonEmpty a -> NonEmpty a
- (!!) :: NonEmpty a -> Int -> a
- 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)
- fromList :: [a] -> NonEmpty a
- toList :: NonEmpty a -> [a]
- nonEmpty :: [a] -> Maybe (NonEmpty a)
- xor :: NonEmpty Bool -> Bool
The type of non-empty streams
Non-empty (and non-strict) list type.
Since: base-4.9.0.0
Constructors
| a :| [a] infixr 5 |
Instances
| MonadFix NonEmpty # | Since: base-4.9.0.0 |
Defined in Control.Monad.Fix | |
| MonadZip NonEmpty # | Since: base-4.9.0.0 |
| Foldable NonEmpty # | Since: base-4.9.0.0 |
Defined in Data.Foldable Methods fold :: Monoid m => NonEmpty m -> m # foldMap :: Monoid m => (a -> m) -> NonEmpty a -> m # foldMap' :: Monoid m => (a -> m) -> NonEmpty a -> m # foldr :: (a -> b -> b) -> b -> NonEmpty a -> b # foldr' :: (a -> b -> b) -> b -> NonEmpty a -> b # foldl :: (b -> a -> b) -> b -> NonEmpty a -> b # foldl' :: (b -> a -> b) -> b -> NonEmpty a -> b # foldr1 :: (a -> a -> a) -> NonEmpty a -> a # foldl1 :: (a -> a -> a) -> NonEmpty a -> a # elem :: Eq a => a -> NonEmpty a -> Bool # maximum :: Ord a => NonEmpty a -> a # minimum :: Ord a => NonEmpty a -> a # | |
| Eq1 NonEmpty # | Since: base-4.10.0.0 |
| Ord1 NonEmpty # | Since: base-4.10.0.0 |
Defined in Data.Functor.Classes | |
| Read1 NonEmpty # | Since: base-4.10.0.0 |
Defined in Data.Functor.Classes | |
| Show1 NonEmpty # | Since: base-4.10.0.0 |
| Traversable NonEmpty # | Since: base-4.9.0.0 |
| Applicative NonEmpty # | Since: base-4.9.0.0 |
| Functor NonEmpty # | Since: base-4.9.0.0 |
| Monad NonEmpty # | Since: base-4.9.0.0 |
| Generic1 NonEmpty # | |
| Data a => Data (NonEmpty a) # | Since: base-4.9.0.0 |
Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> NonEmpty a -> c (NonEmpty a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (NonEmpty a) # toConstr :: NonEmpty a -> Constr # dataTypeOf :: NonEmpty a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (NonEmpty a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (NonEmpty a)) # gmapT :: (forall b. Data b => b -> b) -> NonEmpty a -> NonEmpty a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r # gmapQ :: (forall d. Data d => d -> u) -> NonEmpty a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> NonEmpty a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a) # | |
| Semigroup (NonEmpty a) # | Since: base-4.9.0.0 |
| IsList (NonEmpty a) # | Since: base-4.9.0.0 |
| Generic (NonEmpty a) # | |
| Read a => Read (NonEmpty a) # | Since: base-4.11.0.0 |
| Show a => Show (NonEmpty a) # | Since: base-4.11.0.0 |
| Eq a => Eq (NonEmpty a) # | Since: base-4.9.0.0 |
| Ord a => Ord (NonEmpty a) # | Since: base-4.9.0.0 |
Defined in GHC.Base Methods compare :: NonEmpty a -> NonEmpty a -> Ordering Source # (<) :: NonEmpty a -> NonEmpty a -> Bool Source # (<=) :: NonEmpty a -> NonEmpty a -> Bool Source # (>) :: NonEmpty a -> NonEmpty a -> Bool Source # (>=) :: NonEmpty a -> NonEmpty a -> Bool Source # | |
| type Rep1 NonEmpty # | Since: base-4.6.0.0 |
Defined in GHC.Generics type Rep1 NonEmpty = D1 ('MetaData "NonEmpty" "GHC.Base" "base" 'False) (C1 ('MetaCons ":|" ('InfixI 'LeftAssociative 9) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1 :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 []))) | |
| type Item (NonEmpty a) # | |
| type Rep (NonEmpty a) # | Since: base-4.6.0.0 |
Defined in GHC.Generics type Rep (NonEmpty a) = D1 ('MetaData "NonEmpty" "GHC.Base" "base" 'False) (C1 ('MetaCons ":|" ('InfixI 'LeftAssociative 9) 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [a]))) | |
Non-empty stream transformations
intersperse :: a -> NonEmpty a -> NonEmpty a #
'intersperse x xs' alternates elements of the list with copies of x.
intersperse 0 (1 :| [2,3]) == 1 :| [0,2,0,3]
Basic functions
uncons :: NonEmpty a -> (a, Maybe (NonEmpty a)) #
uncons produces the first element of the stream, and a stream of the
remaining elements, if any.
inits :: Foldable f => f a -> NonEmpty [a] #
The inits function takes a stream xs and returns all the
finite prefixes of xs.
tails :: Foldable f => f a -> NonEmpty [a] #
The tails function takes a stream xs and returns all the
suffixes of xs.
appendList :: NonEmpty a -> [a] -> NonEmpty 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: base-4.16
prependList :: [a] -> NonEmpty a -> NonEmpty a #
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: base-4.16
Building streams
iterate :: (a -> a) -> a -> NonEmpty a #
produces the infinite sequence
of repeated applications of iterate f xf to x.
iterate f x = x :| [f x, f (f x), ..]
cycle :: NonEmpty a -> NonEmpty a #
returns the infinite repetition of cycle xsxs:
cycle (1 :| [2,3]) = 1 :| [2,3,1,2,3,...]
insert :: (Foldable f, Ord a) => a -> f a -> NonEmpty a #
inserts insert x xsx 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.
some1 :: Alternative f => f a -> f (NonEmpty a) #
sequences some1 xx one or more times.
Extracting sublists
drop :: Int -> NonEmpty a -> [a] #
drops the first drop n xsn elements off the front of
the sequence xs.
splitAt :: Int -> NonEmpty a -> ([a], [a]) #
returns a pair consisting of the prefix of splitAt n xsxs
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 xstakeWhile :: (a -> Bool) -> NonEmpty a -> [a] #
returns the longest prefix of the stream
takeWhile p xsxs for which the predicate p holds.
span :: (a -> Bool) -> NonEmpty a -> ([a], [a]) #
returns the longest prefix of span p xsxs 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 xsfilter :: (a -> Bool) -> NonEmpty a -> [a] #
removes any elements from filter p xsxs that do not satisfy p.
partition :: (a -> Bool) -> NonEmpty a -> ([a], [a]) #
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)group :: (Foldable f, Eq a) => f a -> [NonEmpty a] #
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" : ...
groupAllWith :: Ord b => (a -> b) -> [a] -> [NonEmpty a] #
groupAllWith operates like groupWith, but sorts the list
first so that each equivalence class has, at most, one list in the
output
groupWith1 :: Eq b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a) #
groupWith1 is to group1 as groupWith is to group
groupAllWith1 :: Ord b => (a -> b) -> NonEmpty a -> NonEmpty (NonEmpty a) #
groupAllWith1 is to groupWith1 as groupAllWith is to groupWith
Sublist predicates
isPrefixOf :: Eq a => [a] -> NonEmpty a -> Bool #
The isPrefixOf function returns True if the first argument is
a prefix of the second.
"Set" operations
Indexing streams
(!!) :: NonEmpty a -> Int -> a infixl 9 #
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.
Zipping and unzipping streams
zip :: NonEmpty a -> NonEmpty b -> NonEmpty (a, b) #
The zip function takes two streams and returns a stream of
corresponding pairs.
Converting to and from a list
fromList :: [a] -> NonEmpty a #
Converts a normal list to a NonEmpty stream.
Raises an error if given an empty list.