Data.List.Lazy

toUnfoldable :: forall f. Unfoldable f => List ~> f

Convert a list into any unfoldable structure.

Running time: O(n)

fromFoldable :: forall f. Foldable f => f ~> List

Construct a list from a foldable structure.

Running time: O(n)

singleton :: forall a. a -> List a

Create a list with a single element.

Running time: O(1)

Operator alias for Data.List.Lazy.range (non-associative / precedence 8)

An infix synonym for range.

range :: Int -> Int -> List Int

Create a list containing a range of integers, including both endpoints.

replicate :: forall a. Int -> a -> List a

Create a list with repeated instances of a value.

replicateM :: forall m a. Monad m => Int -> m a -> m (List a)

Perform a monadic action n times collecting all of the results.

some :: forall f a. Alternative f => Lazy (f (List a)) => f a -> f (List a)

Attempt a computation multiple times, requiring at least one success.

The Lazy constraint is used to generate the result lazily, to ensure termination.

many :: forall f a. Alternative f => Lazy (f (List a)) => f a -> f (List a)

Attempt a computation multiple times, returning as many successful results as possible (possibly zero).

The Lazy constraint is used to generate the result lazily, to ensure termination.

repeat :: forall a. a -> List a

Create a list by repeating an element

iterate :: forall a. (a -> a) -> a -> List a

Create a list by iterating a function

cycle :: forall a. List a -> List a

Create a list by repeating another list

null :: forall a. List a -> Boolean

Test whether a list is empty.

Running time: O(1)

length :: forall a. List a -> Int

Get the length of a list

Running time: O(n)

snoc :: forall a. List a -> a -> List a

Append an element to the end of a list, creating a new list.

Running time: O(n)

insert :: forall a. Ord a => a -> List a -> List a

Insert an element into a sorted list.

Running time: O(n)

insertBy :: forall a. (a -> a -> Ordering) -> a -> List a -> List a

Insert an element into a sorted list, using the specified function to determine the ordering of elements.

Running time: O(n)

head :: List ~> Maybe

Get the first element in a list, or Nothing if the list is empty.

Running time: O(1).

last :: List ~> Maybe

Get the last element in a list, or Nothing if the list is empty.

Running time: O(n).

tail :: forall a. List a -> Maybe (List a)

Get all but the first element of a list, or Nothing if the list is empty.

Running time: O(1)

init :: forall a. List a -> Maybe (List a)

Get all but the last element of a list, or Nothing if the list is empty.

Running time: O(n)

uncons :: forall a. List a -> Maybe { head :: a, tail :: List a }

Break a list into its first element, and the remaining elements, or Nothing if the list is empty.

Running time: O(1)

Operator alias for Data.List.Lazy.index (left-associative / precedence 8)

An infix synonym for index.

index :: forall a. List a -> Int -> Maybe a

Get the element at the specified index, or Nothing if the index is out-of-bounds.

Running time: O(n) where n is the required index.

elemIndex :: forall a. Eq a => a -> List a -> Maybe Int

Find the index of the first element equal to the specified element.

elemLastIndex :: forall a. Eq a => a -> List a -> Maybe Int

Find the index of the last element equal to the specified element.

findIndex :: forall a. (a -> Boolean) -> List a -> Maybe Int

Find the first index for which a predicate holds.

findLastIndex :: forall a. (a -> Boolean) -> List a -> Maybe Int

Find the last index for which a predicate holds.

insertAt :: forall a. Int -> a -> List a -> List a

Insert an element into a list at the specified index, or append the element to the end of the list if the index is out-of-bounds, returning a new list.

Running time: O(n)

deleteAt :: forall a. Int -> List a -> List a

Delete an element from a list at the specified index, returning a new list, or return the original list unchanged if the index is out-of-bounds.

Running time: O(n)

updateAt :: forall a. Int -> a -> List a -> List a

Update the element at the specified index, returning a new list, or return the original list unchanged if the index is out-of-bounds.

Running time: O(n)

modifyAt :: forall a. Int -> (a -> a) -> List a -> List a

Update the element at the specified index by applying a function to the current value, returning a new list, or return the original list unchanged if the index is out-of-bounds.

Running time: O(n)

alterAt :: forall a. Int -> (a -> Maybe a) -> List a -> List a

Update or delete the element at the specified index by applying a function to the current value, returning a new list, or return the original list unchanged if the index is out-of-bounds.

Running time: O(n)

reverse :: List ~> List

Reverse a list.

Running time: O(n)

concat :: forall a. List (List a) -> List a

Flatten a list of lists.

Running time: O(n), where n is the total number of elements.

concatMap :: forall a b. (a -> List b) -> List a -> List b

Apply a function to each element in a list, and flatten the results into a single, new list.

Running time: O(n), where n is the total number of elements.

filter :: forall a. (a -> Boolean) -> List a -> List a

Filter a list, keeping the elements which satisfy a predicate function.

Running time: O(n)

filterM :: forall a m. Monad m => (a -> m Boolean) -> List a -> m (List a)

Filter where the predicate returns a monadic Boolean.

For example:

powerSet :: forall a. [a] -> [[a]]
powerSet = filterM (const [true, false])

mapMaybe :: forall a b. (a -> Maybe b) -> List a -> List b

Apply a function to each element in a list, keeping only the results which contain a value.

Running time: O(n)

catMaybes :: forall a. List (Maybe a) -> List a

Filter a list of optional values, keeping only the elements which contain a value.

newtype Pattern a

A newtype used in cases where there is a list to be matched.

Constructors

• Pattern (List a)

Instances

• (Eq a) => Eq (Pattern a)
• (Ord a) => Ord (Pattern a)
• Newtype (Pattern a) _
• (Show a) => Show (Pattern a)

stripPrefix :: forall a. Eq a => Pattern a -> List a -> Maybe (List a)

If the list starts with the given prefix, return the portion of the list left after removing it, as a Just value. Otherwise, return Nothing.

• stripPrefix (Pattern (fromFoldable [1])) (fromFoldable [1,2]) == Just (fromFoldable [2])
• stripPrefix (Pattern (fromFoldable [])) (fromFoldable [1]) == Just (fromFoldable [1])
• stripPrefix (Pattern (fromFoldable [2])) (fromFoldable [1]) == Nothing

Running time: O(n) where n is the number of elements to strip.

slice :: Int -> Int -> List ~> List

Extract a sublist by a start and end index.

take :: forall a. Int -> List a -> List a

Take the specified number of elements from the front of a list.

Running time: O(n) where n is the number of elements to take.

takeWhile :: forall a. (a -> Boolean) -> List a -> List a

Take those elements from the front of a list which match a predicate.

Running time (worst case): O(n)

drop :: forall a. Int -> List a -> List a

Drop the specified number of elements from the front of a list.

Running time: O(n) where n is the number of elements to drop.

dropWhile :: forall a. (a -> Boolean) -> List a -> List a

Drop those elements from the front of a list which match a predicate.

Running time (worst case): O(n)

span :: forall a. (a -> Boolean) -> List a -> { init :: List a, rest :: List a }

Split a list into two parts:

1. the longest initial segment for which all elements satisfy the specified predicate
2. the remaining elements

For example,

span (\n -> n % 2 == 1) (1 : 3 : 2 : 4 : 5 : Nil) == Tuple (1 : 3 : Nil) (2 : 4 : 5 : Nil)

Running time: O(n)

group :: forall a. Eq a => List a -> List (NonEmptyList a)

Group equal, consecutive elements of a list into lists.

For example,

group (1 : 1 : 2 : 2 : 1 : Nil) == (1 : 1 : Nil) : (2 : 2 : Nil) : (1 : Nil) : Nil

Running time: O(n)

groupBy :: forall a. (a -> a -> Boolean) -> List a -> List (NonEmptyList a)

Group equal, consecutive elements of a list into lists, using the specified equivalence relation to determine equality.

Running time: O(n)

partition :: forall a. (a -> Boolean) -> List a -> { no :: List a, yes :: List a }

Returns a tuple of lists of elements which do and do not satisfy a predicate, respectively.

Running time: O(n)

nub :: forall a. Ord a => List a -> List a

Remove duplicate elements from a list. Keeps the first occurrence of each element in the input list, in the same order they appear in the input list.

Running time: O(n log n)

nubBy :: forall a. (a -> a -> Ordering) -> List a -> List a

Remove duplicate elements from a list based on the provided comparison function. Keeps the first occurrence of each element in the input list, in the same order they appear in the input list.

Running time: O(n log n)

nubEq :: forall a. Eq a => List a -> List a

Remove duplicate elements from a list.

Running time: O(n^2)

nubByEq :: forall a. (a -> a -> Boolean) -> List a -> List a

Remove duplicate elements from a list, using the specified function to determine equality of elements.

Running time: O(n^2)

union :: forall a. Eq a => List a -> List a -> List a

Calculate the union of two lists.

Running time: O(n^2)

unionBy :: forall a. (a -> a -> Boolean) -> List a -> List a -> List a

Calculate the union of two lists, using the specified function to determine equality of elements.

Running time: O(n^2)

delete :: forall a. Eq a => a -> List a -> List a

Delete the first occurrence of an element from a list.

Running time: O(n)

deleteBy :: forall a. (a -> a -> Boolean) -> a -> List a -> List a

Delete the first occurrence of an element from a list, using the specified function to determine equality of elements.

Running time: O(n)

Operator alias for Data.List.Lazy.difference (non-associative / precedence 5)

difference :: forall a. Eq a => List a -> List a -> List a

Delete the first occurrence of each element in the second list from the first list.

Running time: O(n^2)

intersect :: forall a. Eq a => List a -> List a -> List a

Calculate the intersection of two lists.

Running time: O(n^2)

intersectBy :: forall a. (a -> a -> Boolean) -> List a -> List a -> List a

Calculate the intersection of two lists, using the specified function to determine equality of elements.

Running time: O(n^2)

zipWith :: forall a b c. (a -> b -> c) -> List a -> List b -> List c

Apply a function to pairs of elements at the same positions in two lists, collecting the results in a new list.

If one list is longer, elements will be discarded from the longer list.

For example

zipWith (*) (1 : 2 : 3 : Nil) (4 : 5 : 6 : 7 Nil) == 4 : 10 : 18 : Nil

Running time: O(min(m, n))

zipWithA :: forall m a b c. Applicative m => (a -> b -> m c) -> List a -> List b -> m (List c)

A generalization of zipWith which accumulates results in some Applicative functor.

zip :: forall a b. List a -> List b -> List (Tuple a b)

Collect pairs of elements at the same positions in two lists.

Running time: O(min(m, n))

unzip :: forall a b. List (Tuple a b) -> Tuple (List a) (List b)

Transforms a list of pairs into a list of first components and a list of second components.

transpose :: forall a. List (List a) -> List (List a)

The 'transpose' function transposes the rows and columns of its argument. For example,

transpose ((1:2:3:nil) : (4:5:6:nil) : nil) ==
  ((1:4:nil) : (2:5:nil) : (3:6:nil) : nil)

If some of the rows are shorter than the following rows, their elements are skipped:

transpose ((10:11:nil) : (20:nil) : nil : (30:31:32:nil) : nil) ==
  ((10:20:30:nil) : (11:31:nil) : (32:nil) : nil)

foldM :: forall m a b. Monad m => (b -> a -> m b) -> b -> List a -> m b

Perform a fold using a monadic step function.

foldrLazy :: forall a b. Lazy b => (a -> b -> b) -> b -> List a -> b

Perform a right fold lazily

scanlLazy :: forall a b. (b -> a -> b) -> b -> List a -> List b

Perform a left scan lazily

foldMap :: forall f a m. Foldable f => Monoid m => (a -> m) -> f a -> m

foldl :: forall f a b. Foldable f => (b -> a -> b) -> b -> f a -> b

foldr :: forall f a b. Foldable f => (a -> b -> b) -> b -> f a -> b

notElem :: forall a f. Foldable f => Eq a => a -> f a -> Boolean

Test whether a value is not an element of a data structure.

intercalate :: forall f m. Foldable f => Monoid m => m -> f m -> m

Fold a data structure, accumulating values in some Monoid, combining adjacent elements using the specified separator.

For example:

> intercalate ", " ["Lorem", "ipsum", "dolor"]
= "Lorem, ipsum, dolor"

> intercalate "*" ["a", "b", "c"]
= "a*b*c"

> intercalate [1] [[2, 3], [4, 5], [6, 7]]
= [2, 3, 1, 4, 5, 1, 6, 7]

fold :: forall f m. Foldable f => Monoid m => f m -> m

Fold a data structure, accumulating values in some Monoid.

findMap :: forall a b f. Foldable f => (a -> Maybe b) -> f a -> Maybe b

Try to find an element in a data structure which satisfies a predicate mapping.

find :: forall a f. Foldable f => (a -> Boolean) -> f a -> Maybe a

Try to find an element in a data structure which satisfies a predicate.

elem :: forall a f. Foldable f => Eq a => a -> f a -> Boolean

Test whether a value is an element of a data structure.

any :: forall a b f. Foldable f => HeytingAlgebra b => (a -> b) -> f a -> b

any f is the same as or <<< map f; map a function over the structure, and then get the disjunction of the results.

all :: forall a b f. Foldable f => HeytingAlgebra b => (a -> b) -> f a -> b

all f is the same as and <<< map f; map a function over the structure, and then get the conjunction of the results.

data Step a

A list is either empty (represented by the Nil constructor) or non-empty, in which case it consists of a head element, and another list (represented by the Cons constructor).

Constructors

• Nil
• Cons a (List a)

Instances

• (Show a) => Show (Step a)

newtype List a

A lazy linked list.

Constructors

• List (Lazy (Step a))

Instances

• Newtype (List a) _
• (Show a) => Show (List a)
• (Eq a) => Eq (List a)
• Eq1 List
• (Ord a) => Ord (List a)
• Ord1 List
• Lazy (List a)
• Semigroup (List a)
• Monoid (List a)
• Functor List
• FunctorWithIndex Int List
• Foldable List
• FoldableWithIndex Int List
• Unfoldable1 List
• Unfoldable List
• Traversable List
• TraversableWithIndex Int List
• Apply List
• Applicative List
• Bind List
• Monad List
• Alt List
• Plus List
• Alternative List
• MonadZero List
• MonadPlus List
• Extend List

step :: forall a. List a -> Step a

Unwrap a lazy linked list

nil :: forall a. List a

The empty list.

Running time: O(1)

cons :: forall a. a -> List a -> List a

Attach an element to the front of a lazy list.

Running time: O(1)

Operator alias for Data.List.Lazy.Types.cons (right-associative / precedence 6)

An infix alias for cons; attaches an element to the front of a list.

Running time: O(1)

scanr :: forall a b f. Traversable f => (a -> b -> b) -> b -> f a -> f b

Fold a data structure from the right, keeping all intermediate results instead of only the final result. Note that the initial value does not appear in the result (unlike Haskell's Prelude.scanr).

scanr (+) 0 [1,2,3] = [6,5,3]
scanr (flip (-)) 10 [1,2,3] = [4,5,7]

scanl :: forall a b f. Traversable f => (b -> a -> b) -> b -> f a -> f b

Fold a data structure from the left, keeping all intermediate results instead of only the final result. Note that the initial value does not appear in the result (unlike Haskell's Prelude.scanl).

scanl (+) 0  [1,2,3] = [1,3,6]
scanl (-) 10 [1,2,3] = [9,7,4]