Data.ListLike.Base

Generic operations over list-like structures

Written by John Goerzen, [e-mail]

Documentation

class (FoldableLL full item, Monoid full) => ListLike full item | full -> item where

The class implementing list-like functions.

It is worth noting that types such as Map can be instances of ListLike. Due to their specific ways of operating, they may not behave in the expected way in some cases. For instance, cons may not increase the size of a map if the key you have given is already in the map; it will just replace the value already there.

Implementators must define at least:

• singleton
• head
• tail
• null or genericLength

Minimal complete definition

singleton, head, tail

Methods

empty :: full

The empty list

singleton :: item -> full

Creates a single-element list out of an element

cons :: item -> full -> full

Like (:) for lists: adds an element to the beginning of a list

snoc :: full -> item -> full

Adds an element to the *end* of a ListLike.

append :: full -> full -> full

Combines two lists. Like (++).

head :: full -> item

Extracts the first element of a ListLike.

last :: full -> item

Extracts the last element of a ListLike.

tail :: full -> full

Gives all elements after the head.

init :: full -> full

All elements of the list except the last one. See also inits.

null :: full -> Bool

Tests whether the list is empty.

length :: full -> Int

Length of the list. See also genericLength.

map :: ListLike full' item' => (item -> item') -> full -> full'

Apply a function to each element, returning any other valid ListLike. rigidMap will always be at least as fast, if not faster, than this function and is recommended if it will work for your purposes. See also mapM.

rigidMap :: (item -> item) -> full -> full

Like map, but without the possibility of changing the type of the item. This can have performance benefits for things such as ByteStrings, since it will let the ByteString use its native low-level map implementation.

reverse :: full -> full

Reverse the elements in a list.

intersperse :: item -> full -> full

Add an item between each element in the structure

concat :: (ListLike full' full, Monoid full) => full' -> full

Flatten the structure.

concatMap :: ListLike full' item' => (item -> full') -> full -> full'

Map a function over the items and concatenate the results. See also rigidConcatMap.

rigidConcatMap :: (item -> full) -> full -> full

Like concatMap, but without the possibility of changing the type of the item. This can have performance benefits for some things such as ByteString.

any :: (item -> Bool) -> full -> Bool

True if any items satisfy the function

all :: (item -> Bool) -> full -> Bool

True if all items satisfy the function

maximum :: Ord item => full -> item

The maximum value of the list

minimum :: Ord item => full -> item

The minimum value of the list

replicate :: Int -> item -> full

Generate a structure with the specified length with every element set to the item passed in. See also genericReplicate

take :: Int -> full -> full

Takes the first n elements of the list. See also genericTake.

drop :: Int -> full -> full

Drops the first n elements of the list. See also genericDrop

splitAt :: Int -> full -> (full, full)

Equivalent to (take n xs, drop n xs). See also genericSplitAt.

takeWhile :: (item -> Bool) -> full -> full

Returns all elements at start of list that satisfy the function.

dropWhile :: (item -> Bool) -> full -> full

Drops all elements from the start of the list that satisfy the function.

dropWhileEnd :: (item -> Bool) -> full -> full

Drops all elements from the end of the list that satisfy the function.

span :: (item -> Bool) -> full -> (full, full)

The equivalent of (takeWhile f xs, dropWhile f xs)

break :: (item -> Bool) -> full -> (full, full)

The equivalent of span (not . f)

group :: (ListLike full' full, Eq item) => full -> full'

Split a list into sublists, each which contains equal arguments. For order-preserving types, concatenating these sublists will produce the original list. See also groupBy.

inits :: ListLike full' full => full -> full'

All initial segments of the list, shortest first

tails :: ListLike full' full => full -> full'

All final segnemts, longest first

isPrefixOf :: Eq item => full -> full -> Bool

True when the first list is at the beginning of the second.

isSuffixOf :: Eq item => full -> full -> Bool

True when the first list is at the beginning of the second.

isInfixOf :: Eq item => full -> full -> Bool

True when the first list is wholly containted within the second

elem :: Eq item => item -> full -> Bool

True if the item occurs in the list

notElem :: Eq item => item -> full -> Bool

True if the item does not occur in the list

find :: (item -> Bool) -> full -> Maybe item

Take a function and return the first matching element, or Nothing if there is no such element.

filter :: (item -> Bool) -> full -> full

Returns only the elements that satisfy the function.

partition :: (item -> Bool) -> full -> (full, full)

Returns the lists that do and do not satisfy the function. Same as (filter p xs, filter (not . p) xs)

index :: full -> Int -> item

The element at 0-based index i. Raises an exception if i is out of bounds. Like (!!) for lists.

elemIndex :: Eq item => item -> full -> Maybe Int

Returns the index of the element, if it exists.

elemIndices :: (Eq item, ListLike result Int) => item -> full -> result

Returns the indices of the matching elements. See also findIndices

findIndex :: (item -> Bool) -> full -> Maybe Int

Take a function and return the index of the first matching element, or Nothing if no element matches

findIndices :: ListLike result Int => (item -> Bool) -> full -> result

Returns the indices of all elements satisfying the function

sequence :: (Monad m, ListLike fullinp (m item)) => fullinp -> m full

Evaluate each action in the sequence and collect the results

mapM :: (Monad m, ListLike full' item') => (item -> m item') -> full -> m full'

A map in monad space. Same as sequence . map

See also rigidMapM

rigidMapM :: Monad m => (item -> m item) -> full -> m full

Like mapM, but without the possibility of changing the type of the item. This can have performance benefits with some types.

nub :: Eq item => full -> full

Removes duplicate elements from the list. See also nubBy

delete :: Eq item => item -> full -> full

Removes the first instance of the element from the list. See also deleteBy

deleteFirsts :: Eq item => full -> full -> full

List difference. Removes from the first list the first instance of each element of the second list. See '(\)' and deleteFirstsBy

union :: Eq item => full -> full -> full

List union: the set of elements that occur in either list. Duplicate elements in the first list will remain duplicate. See also unionBy.

intersect :: Eq item => full -> full -> full

List intersection: the set of elements that occur in both lists. See also intersectBy

sort :: Ord item => full -> full

Sorts the list. On data types that do not preserve ordering, or enforce their own ordering, the result may not be what you expect. See also sortBy.

insert :: Ord item => item -> full -> full

Inserts the element at the last place where it is still less than or equal to the next element. On data types that do not preserve ordering, or enforce their own ordering, the result may not be what you expect. On types such as maps, this may result in changing an existing item. See also insertBy.

toList :: full -> [item]

Converts the structure to a list. This is logically equivolent to fromListLike, but may have a more optimized implementation.

fromList :: [item] -> full

Generates the structure from a list.

fromListLike :: ListLike full' item => full -> full'

Converts one ListLike to another. See also toList. Default implementation is fromListLike = map id

nubBy :: (item -> item -> Bool) -> full -> full

Generic version of nub

deleteBy :: (item -> item -> Bool) -> item -> full -> full

Generic version of deleteBy

deleteFirstsBy :: (item -> item -> Bool) -> full -> full -> full

Generic version of deleteFirsts

unionBy :: (item -> item -> Bool) -> full -> full -> full

Generic version of union

intersectBy :: (item -> item -> Bool) -> full -> full -> full

Generic version of intersect

groupBy :: (ListLike full' full, Eq item) => (item -> item -> Bool) -> full -> full'

Generic version of group.

sortBy :: (item -> item -> Ordering) -> full -> full

Sort function taking a custom comparison function

insertBy :: (item -> item -> Ordering) -> item -> full -> full

Like insert, but with a custom comparison function

genericLength :: Num a => full -> a

Length of the list

genericTake :: Integral a => a -> full -> full

Generic version of take

genericDrop :: Integral a => a -> full -> full

Generic version of drop

genericSplitAt :: Integral a => a -> full -> (full, full)

Generic version of splitAt

genericReplicate :: Integral a => a -> item -> full

Generic version of replicate

Instances

ListLike CharStringLazy Char

ListLike CharString Char

ListLike [a] a

class ListLike full item => InfiniteListLike full item | full -> item where

An extension to ListLike for those data types that are capable of dealing with infinite lists. Some ListLike functions are capable of working with finite or infinite lists. The functions here require infinite list capability in order to work at all.

Minimal complete definition

Nothing

Methods

iterate :: (item -> item) -> item -> full

An infinite list of repeated calls of the function to args

repeat :: item -> full

An infinite list where each element is the same

cycle :: full -> full

Converts a finite list into a circular one

zip :: (ListLike full item, ListLike fullb itemb, ListLike result (item, itemb)) => full -> fullb -> result

Takes two lists and returns a list of corresponding pairs.

zipWith :: (ListLike full item, ListLike fullb itemb, ListLike result resultitem) => (item -> itemb -> resultitem) -> full -> fullb -> result

Takes two lists and combines them with a custom combining function

sequence_ :: (Monad m, FoldableLL full (m item)) => full -> m ()

Evaluate each action, ignoring the results. Same as mapM_ id.