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 |
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]
- (<|) :: 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]
- 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
a :| [a] infixr 5 |
Instances
Monad NonEmpty # | Since: base-4.9.0.0 |
Functor NonEmpty # | Since: base-4.9.0.0 |
MonadFix NonEmpty # | Since: base-4.9.0.0 |
Defined in Control.Monad.Fix | |
Applicative NonEmpty # | Since: base-4.9.0.0 |
Foldable NonEmpty # | Since: base-4.9.0.0 |
Defined in Data.Foldable 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 # | |
Traversable NonEmpty # | Since: base-4.9.0.0 |
MonadZip NonEmpty # | Since: base-4.9.0.0 |
Show1 NonEmpty # | Since: base-4.10.0.0 |
Read1 NonEmpty # | Since: base-4.10.0.0 |
Defined in Data.Functor.Classes | |
Ord1 NonEmpty # | Since: base-4.10.0.0 |
Defined in Data.Functor.Classes | |
Eq1 NonEmpty # | Since: base-4.10.0.0 |
IsList (NonEmpty a) # | Since: base-4.9.0.0 |
Eq a => Eq (NonEmpty a) # | Since: base-4.9.0.0 |
Data a => Data (NonEmpty a) # | Since: base-4.9.0.0 |
Defined in Data.Data 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) # | |
Ord a => Ord (NonEmpty a) # | Since: base-4.9.0.0 |
Defined in GHC.Base 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 # | |
Read a => Read (NonEmpty a) # | Since: base-4.11.0.0 |
Show a => Show (NonEmpty a) # | Since: base-4.11.0.0 |
Generic (NonEmpty a) # | Since: base-4.6.0.0 |
Semigroup (NonEmpty a) # | Since: base-4.9.0.0 |
Generic1 NonEmpty # | Since: base-4.6.0.0 |
type Rep (NonEmpty a) # | |
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]))) | |
type Item (NonEmpty a) # | |
type Rep1 NonEmpty # | |
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 []))) |
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
.
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 xs
takeWhile :: (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 xs
filter :: (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.