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| Data.List | | Portability | portable | | Stability | stable | | Maintainer | libraries@haskell.org |
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| Description |
| Operations on lists.
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| Synopsis |
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| (++) :: [a] -> [a] -> [a] | | | head :: [a] -> a | | | last :: [a] -> a | | | tail :: [a] -> [a] | | | init :: [a] -> [a] | | | null :: [a] -> Bool | | | length :: [a] -> Int | | | map :: (a -> b) -> [a] -> [b] | | | reverse :: [a] -> [a] | | | intersperse :: a -> [a] -> [a] | | | transpose :: [[a]] -> [[a]] | | | foldl :: (a -> b -> a) -> a -> [b] -> a | | | foldl' :: (a -> b -> a) -> a -> [b] -> a | | | foldl1 :: (a -> a -> a) -> [a] -> a | | | foldr :: (a -> b -> b) -> b -> [a] -> b | | | foldr1 :: (a -> a -> a) -> [a] -> a | | | concat :: [[a]] -> [a] | | | concatMap :: (a -> [b]) -> [a] -> [b] | | | and :: [Bool] -> Bool | | | or :: [Bool] -> Bool | | | any :: (a -> Bool) -> [a] -> Bool | | | all :: (a -> Bool) -> [a] -> Bool | | | sum :: Num a => [a] -> a | | | product :: Num a => [a] -> a | | | maximum :: Ord a => [a] -> a | | | minimum :: Ord a => [a] -> a | | | scanl :: (a -> b -> a) -> a -> [b] -> [a] | | | scanl1 :: (a -> a -> a) -> [a] -> [a] | | | scanr :: (a -> b -> b) -> b -> [a] -> [b] | | | scanr1 :: (a -> a -> a) -> [a] -> [a] | | | mapAccumL :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y]) | | | mapAccumR :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y]) | | | iterate :: (a -> a) -> a -> [a] | | | repeat :: a -> [a] | | | replicate :: Int -> a -> [a] | | | cycle :: [a] -> [a] | | | unfoldr :: (b -> Maybe (a, b)) -> b -> [a] | | | take :: Int -> [a] -> [a] | | | drop :: Int -> [a] -> [a] | | | splitAt :: Int -> [a] -> ([a], [a]) | | | takeWhile :: (a -> Bool) -> [a] -> [a] | | | dropWhile :: (a -> Bool) -> [a] -> [a] | | | span :: (a -> Bool) -> [a] -> ([a], [a]) | | | break :: (a -> Bool) -> [a] -> ([a], [a]) | | | group :: Eq a => [a] -> [[a]] | | | inits :: [a] -> [[a]] | | | tails :: [a] -> [[a]] | | | isPrefixOf :: Eq a => [a] -> [a] -> Bool | | | isSuffixOf :: Eq a => [a] -> [a] -> Bool | | | elem :: Eq a => a -> [a] -> Bool | | | notElem :: Eq a => a -> [a] -> Bool | | | lookup :: Eq a => a -> [(a, b)] -> Maybe b | | | find :: (a -> Bool) -> [a] -> Maybe a | | | filter :: (a -> Bool) -> [a] -> [a] | | | partition :: (a -> Bool) -> [a] -> ([a], [a]) | | | (!!) :: [a] -> Int -> a | | | elemIndex :: Eq a => a -> [a] -> Maybe Int | | | elemIndices :: Eq a => a -> [a] -> [Int] | | | findIndex :: (a -> Bool) -> [a] -> Maybe Int | | | findIndices :: (a -> Bool) -> [a] -> [Int] | | | zip :: [a] -> [b] -> [(a, b)] | | | zip3 :: [a] -> [b] -> [c] -> [(a, b, c)] | | | zip4 :: [a] -> [b] -> [c] -> [d] -> [(a, b, c, d)] | | | zip5 :: [a] -> [b] -> [c] -> [d] -> [e] -> [(a, b, c, d, e)] | | | zip6 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [(a, b, c, d, e, f)] | | | zip7 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [(a, b, c, d, e, f, g)] | | | zipWith :: (a -> b -> c) -> [a] -> [b] -> [c] | | | zipWith3 :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d] | | | zipWith4 :: (a -> b -> c -> d -> e) -> [a] -> [b] -> [c] -> [d] -> [e] | | | zipWith5 :: (a -> b -> c -> d -> e -> f) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] | | | zipWith6 :: (a -> b -> c -> d -> e -> f -> g) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] | | | zipWith7 :: (a -> b -> c -> d -> e -> f -> g -> h) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [h] | | | unzip :: [(a, b)] -> ([a], [b]) | | | unzip3 :: [(a, b, c)] -> ([a], [b], [c]) | | | unzip4 :: [(a, b, c, d)] -> ([a], [b], [c], [d]) | | | unzip5 :: [(a, b, c, d, e)] -> ([a], [b], [c], [d], [e]) | | | unzip6 :: [(a, b, c, d, e, f)] -> ([a], [b], [c], [d], [e], [f]) | | | unzip7 :: [(a, b, c, d, e, f, g)] -> ([a], [b], [c], [d], [e], [f], [g]) | | | lines :: String -> [String] | | | words :: String -> [String] | | | unlines :: [String] -> String | | | unwords :: [String] -> String | | | nub :: Eq a => [a] -> [a] | | | delete :: Eq a => a -> [a] -> [a] | | | (\\) :: Eq a => [a] -> [a] -> [a] | | | union :: Eq a => [a] -> [a] -> [a] | | | intersect :: Eq a => [a] -> [a] -> [a] | | | sort :: Ord a => [a] -> [a] | | | insert :: Ord a => a -> [a] -> [a] | | | nubBy :: (a -> a -> Bool) -> [a] -> [a] | | | deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a] | | | deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] | | | unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] | | | intersectBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] | | | groupBy :: (a -> a -> Bool) -> [a] -> [[a]] | | | sortBy :: (a -> a -> Ordering) -> [a] -> [a] | | | insertBy :: (a -> a -> Ordering) -> a -> [a] -> [a] | | | maximumBy :: (a -> a -> Ordering) -> [a] -> a | | | minimumBy :: (a -> a -> Ordering) -> [a] -> a | | | genericLength :: Num i => [b] -> i | | | genericTake :: Integral i => i -> [a] -> [a] | | | genericDrop :: Integral i => i -> [a] -> [a] | | | genericSplitAt :: Integral i => i -> [b] -> ([b], [b]) | | | genericIndex :: Integral a => [b] -> a -> b | | | genericReplicate :: Integral i => i -> a -> [a] |
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| Basic functions |
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| (++) :: [a] -> [a] -> [a] |
Append two lists, i.e.,
[x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
[x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
If the first list is not finite, the result is the first list. |
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| head :: [a] -> a |
| Extract the first element of a list, which must be non-empty. |
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| last :: [a] -> a |
| Extract the last element of a list, which must be finite and non-empty. |
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| tail :: [a] -> [a] |
| Extract the elements after the head of a list, which must be non-empty. |
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| init :: [a] -> [a] |
| Return all the elements of a list except the last one.
The list must be finite and non-empty. |
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| null :: [a] -> Bool |
| Test whether a list is empty. |
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| length :: [a] -> Int |
| length returns the length of a finite list as an Int.
It is an instance of the more general genericLength,
the result type of which may be any kind of number. |
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| List transformations |
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| map :: (a -> b) -> [a] -> [b] |
map f xs is the list obtained by applying f to each element
of xs, i.e.,
map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
map f [x1, x2, ...] == [f x1, f x2, ...] |
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| reverse :: [a] -> [a] |
| reverse xs returns the elements of xs in reverse order.
xs must be finite. |
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| intersperse :: a -> [a] -> [a] |
The intersperse function takes an element and a list and
`intersperses' that element between the elements of the list.
For example,
intersperse ',' "abcde" == "a,b,c,d,e" |
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| transpose :: [[a]] -> [[a]] |
The transpose function transposes the rows and columns of its argument.
For example,
transpose [[1,2,3],[4,5,6]] == [[1,4],[2,5],[3,6]] |
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| Reducing lists (folds) |
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| foldl :: (a -> b -> a) -> a -> [b] -> a |
foldl, applied to a binary operator, a starting value (typically
the left-identity of the operator), and a list, reduces the list
using the binary operator, from left to right:
foldl f z [x1, x2, ..., xn] == (...((z `f` x1) `f` x2) `f`...) `f` xn
The list must be finite. |
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| foldl' :: (a -> b -> a) -> a -> [b] -> a |
| A strict version of foldl. |
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| foldl1 :: (a -> a -> a) -> [a] -> a |
| foldl1 is a variant of foldl that has no starting value argument,
and thus must be applied to non-empty lists. |
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| foldr :: (a -> b -> b) -> b -> [a] -> b |
foldr, applied to a binary operator, a starting value (typically
the right-identity of the operator), and a list, reduces the list
using the binary operator, from right to left:
foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...) |
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| foldr1 :: (a -> a -> a) -> [a] -> a |
| foldr1 is a variant of foldr that has no starting value argument,
and thus must be applied to non-empty lists. |
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| Special folds |
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| concat :: [[a]] -> [a] |
| Concatenate a list of lists. |
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| concatMap :: (a -> [b]) -> [a] -> [b] |
| Map a function over a list and concatenate the results. |
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| and :: [Bool] -> Bool |
| and returns the conjunction of a Boolean list. For the result to be
True, the list must be finite; False, however, results from a False
value at a finite index of a finite or infinite list. |
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| or :: [Bool] -> Bool |
| or returns the disjunction of a Boolean list. For the result to be
False, the list must be finite; True, however, results from a True
value at a finite index of a finite or infinite list. |
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| any :: (a -> Bool) -> [a] -> Bool |
| Applied to a predicate and a list, any determines if any element
of the list satisfies the predicate. |
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| all :: (a -> Bool) -> [a] -> Bool |
| Applied to a predicate and a list, all determines if all elements
of the list satisfy the predicate. |
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| sum :: Num a => [a] -> a |
| The sum function computes the sum of a finite list of numbers. |
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| product :: Num a => [a] -> a |
| The product function computes the product of a finite list of numbers. |
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| maximum :: Ord a => [a] -> a |
| maximum returns the maximum value from a list,
which must be non-empty, finite, and of an ordered type.
It is a special case of maximumBy, which allows the
programmer to supply their own comparison function. |
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| minimum :: Ord a => [a] -> a |
| minimum returns the minimum value from a list,
which must be non-empty, finite, and of an ordered type.
It is a special case of minimumBy, which allows the
programmer to supply their own comparison function. |
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| Building lists |
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| Scans |
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| scanl :: (a -> b -> a) -> a -> [b] -> [a] |
scanl is similar to foldl, but returns a list 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. |
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| scanl1 :: (a -> a -> a) -> [a] -> [a] |
scanl1 is a variant of scanl that has no starting value argument:
scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...] |
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| scanr :: (a -> b -> b) -> b -> [a] -> [b] |
scanr is the right-to-left dual of scanl.
Note that
head (scanr f z xs) == foldr f z xs. |
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| scanr1 :: (a -> a -> a) -> [a] -> [a] |
| scanr1 is a variant of scanr that has no starting value argument. |
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| Accumulating maps |
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| mapAccumL :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y]) |
| The mapAccumL function behaves like a combination of map and
foldl; it applies a function to each element of a list, passing
an accumulating parameter from left to right, and returning a final
value of this accumulator together with the new list. |
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| mapAccumR :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y]) |
| The mapAccumR function behaves like a combination of map and
foldr; it applies a function to each element of a list, passing
an accumulating parameter from right to left, and returning a final
value of this accumulator together with the new list. |
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| Infinite lists |
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| iterate :: (a -> a) -> a -> [a] |
iterate f x returns an infinite list of repeated applications
of f to x:
iterate f x == [x, f x, f (f x), ...] |
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| repeat :: a -> [a] |
| repeat x is an infinite list, with x the value of every element. |
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| replicate :: Int -> a -> [a] |
| replicate n x is a list of length n with x the value of
every element.
It is an instance of the more general genericReplicate,
in which n may be of any integral type. |
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| cycle :: [a] -> [a] |
| cycle ties a finite list into a circular one, or equivalently,
the infinite repetition of the original list. It is the identity
on infinite lists. |
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| Unfolding |
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| unfoldr :: (b -> Maybe (a, b)) -> b -> [a] |
The unfoldr function is a `dual' to foldr: while foldr
reduces a list to a summary value, unfoldr builds a list from
a seed value. The function takes the element and returns Nothing
if it is done producing the list or returns Just (a,b), in which
case, a is a prepended to the list and b is used as the next
element in a recursive call. For example,
iterate f == unfoldr (\x -> Just (x, f x))
In some cases, unfoldr can undo a foldr operation:
unfoldr f' (foldr f z xs) == xs
if the following holds:
f' (f x y) = Just (x,y)
f' z = Nothing |
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| Sublists |
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| Extracting sublists |
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| take :: Int -> [a] -> [a] |
| take n, applied to a list xs, returns the prefix of xs
of length n, or xs itself if n > length xs.
It is an instance of the more general genericTake,
in which n may be of any integral type. |
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| drop :: Int -> [a] -> [a] |
| drop n xs returns the suffix of xs
after the first n elements, or [] if n > length xs.
It is an instance of the more general genericDrop,
in which n may be of any integral type. |
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| splitAt :: Int -> [a] -> ([a], [a]) |
| splitAt n xs is equivalent to (take n xs, drop n xs).
It is an instance of the more general genericSplitAt,
in which n may be of any integral type. |
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| takeWhile :: (a -> Bool) -> [a] -> [a] |
| takeWhile, applied to a predicate p and a list xs, returns the
longest prefix (possibly empty) of xs of elements that satisfy p. |
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| dropWhile :: (a -> Bool) -> [a] -> [a] |
| dropWhile p xs returns the suffix remaining after takeWhile p xs. |
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| span :: (a -> Bool) -> [a] -> ([a], [a]) |
| span p xs is equivalent to (takeWhile p xs, dropWhile p xs) |
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| break :: (a -> Bool) -> [a] -> ([a], [a]) |
| break p is equivalent to span (not . p). |
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| group :: Eq a => [a] -> [[a]] |
The group function takes a list and returns a list of lists such
that the concatenation of the result is equal to the argument. Moreover,
each sublist in the result contains only equal elements. For example,
group "Mississippi" = ["M","i","ss","i","ss","i","pp","i"]
It is a special case of groupBy, which allows the programmer to supply
their own equality test. |
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| inits :: [a] -> [[a]] |
The inits function returns all initial segments of the argument,
shortest first. For example,
inits "abc" == ["","a","ab","abc"]
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| tails :: [a] -> [[a]] |
The tails function returns all final segments of the argument,
longest first. For example,
tails "abc" == ["abc", "bc", "c",""]
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| Predicates |
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| isPrefixOf :: Eq a => [a] -> [a] -> Bool |
| The isPrefixOf function takes two lists and returns True
iff the first list is a prefix of the second. |
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| isSuffixOf :: Eq a => [a] -> [a] -> Bool |
| The isSuffixOf function takes two lists and returns True
iff the first list is a suffix of the second.
Both lists must be finite. |
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| Searching lists |
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| Searching by equality |
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| elem :: Eq a => a -> [a] -> Bool |
| elem is the list membership predicate, usually written in infix form,
e.g., x elem xs. |
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| notElem :: Eq a => a -> [a] -> Bool |
| notElem is the negation of elem. |
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| lookup :: Eq a => a -> [(a, b)] -> Maybe b |
| lookup key assocs looks up a key in an association list. |
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| Searching with a predicate |
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| find :: (a -> Bool) -> [a] -> Maybe a |
| The find function takes a predicate and a list and returns the
first element in the list matching the predicate, or Nothing if
there is no such element. |
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| filter :: (a -> Bool) -> [a] -> [a] |
filter, applied to a predicate and a list, returns the list of
those elements that satisfy the predicate; i.e.,
filter p xs = [ x | x <- xs, p x] |
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| partition :: (a -> Bool) -> [a] -> ([a], [a]) |
The partition function takes a predicate a list and returns
the pair of lists of elements which do and do not satisfy the
predicate, respectively; i.e.,
partition p xs == (filter p xs, filter (not . p) xs) |
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| Indexing lists |
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| These functions treat a list xs as a indexed collection,
with indices ranging from 0 to length xs - 1. |
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| (!!) :: [a] -> Int -> a |
| List index (subscript) operator, starting from 0.
It is an instance of the more general genericIndex,
which takes an index of any integral type. |
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| elemIndex :: Eq a => a -> [a] -> Maybe Int |
| The elemIndex function returns the index of the first element
in the given list which is equal (by ==) to the query element,
or Nothing if there is no such element. |
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| elemIndices :: Eq a => a -> [a] -> [Int] |
| The elemIndices function extends elemIndex, by returning the
indices of all elements equal to the query element, in ascending order. |
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| findIndex :: (a -> Bool) -> [a] -> Maybe Int |
| The findIndex function takes a predicate and a list and returns
the index of the first element in the list satisfying the predicate,
or Nothing if there is no such element. |
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| findIndices :: (a -> Bool) -> [a] -> [Int] |
| The findIndices function extends findIndex, by returning the
indices of all elements satisfying the predicate, in ascending order. |
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| Zipping and unzipping lists |
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| zip :: [a] -> [b] -> [(a, b)] |
| zip takes two lists and returns a list of corresponding pairs.
If one input list is short, excess elements of the longer list are
discarded. |
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| zip3 :: [a] -> [b] -> [c] -> [(a, b, c)] |
| zip3 takes three lists and returns a list of triples, analogous to
zip. |
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| zip4 :: [a] -> [b] -> [c] -> [d] -> [(a, b, c, d)] |
| The zip4 function takes four lists and returns a list of
quadruples, analogous to zip. |
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| zip5 :: [a] -> [b] -> [c] -> [d] -> [e] -> [(a, b, c, d, e)] |
| The zip5 function takes five lists and returns a list of
five-tuples, analogous to zip. |
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| zip6 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [(a, b, c, d, e, f)] |
| The zip6 function takes six lists and returns a list of six-tuples,
analogous to zip. |
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| zip7 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [(a, b, c, d, e, f, g)] |
| The zip7 function takes seven lists and returns a list of
seven-tuples, analogous to zip. |
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| zipWith :: (a -> b -> c) -> [a] -> [b] -> [c] |
| zipWith generalises zip by zipping with the function given
as the first argument, instead of a tupling function.
For example, zipWith (+) is applied to two lists to produce the
list of corresponding sums. |
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| zipWith3 :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d] |
| The zipWith3 function takes a function which combines three
elements, as well as three lists and returns a list of their point-wise
combination, analogous to zipWith. |
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| zipWith4 :: (a -> b -> c -> d -> e) -> [a] -> [b] -> [c] -> [d] -> [e] |
| The zipWith4 function takes a function which combines four
elements, as well as four lists and returns a list of their point-wise
combination, analogous to zipWith. |
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| zipWith5 :: (a -> b -> c -> d -> e -> f) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] |
| The zipWith5 function takes a function which combines five
elements, as well as five lists and returns a list of their point-wise
combination, analogous to zipWith. |
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| zipWith6 :: (a -> b -> c -> d -> e -> f -> g) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] |
| The zipWith6 function takes a function which combines six
elements, as well as six lists and returns a list of their point-wise
combination, analogous to zipWith. |
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| zipWith7 :: (a -> b -> c -> d -> e -> f -> g -> h) -> [a] -> [b] -> [c] -> [d] -> [e] -> [f] -> [g] -> [h] |
| The zipWith7 function takes a function which combines seven
elements, as well as seven lists and returns a list of their point-wise
combination, analogous to zipWith. |
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| unzip :: [(a, b)] -> ([a], [b]) |
| unzip transforms a list of pairs into a list of first components
and a list of second components. |
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| unzip3 :: [(a, b, c)] -> ([a], [b], [c]) |
| The unzip3 function takes a list of triples and returns three
lists, analogous to unzip. |
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| unzip4 :: [(a, b, c, d)] -> ([a], [b], [c], [d]) |
| The unzip4 function takes a list of quadruples and returns four
lists, analogous to unzip. |
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| unzip5 :: [(a, b, c, d, e)] -> ([a], [b], [c], [d], [e]) |
| The unzip5 function takes a list of five-tuples and returns five
lists, analogous to unzip. |
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| unzip6 :: [(a, b, c, d, e, f)] -> ([a], [b], [c], [d], [e], [f]) |
| The unzip6 function takes a list of six-tuples and returns six
lists, analogous to unzip. |
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| unzip7 :: [(a, b, c, d, e, f, g)] -> ([a], [b], [c], [d], [e], [f], [g]) |
| The unzip7 function takes a list of seven-tuples and returns
seven lists, analogous to unzip. |
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| Special lists |
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| Functions on strings |
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| lines :: String -> [String] |
| lines breaks a string up into a list of strings at newline
characters. The resulting strings do not contain newlines. |
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| words :: String -> [String] |
| words breaks a string up into a list of words, which were delimited
by white space. |
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| unlines :: [String] -> String |
| unlines is an inverse operation to lines.
It joins lines, after appending a terminating newline to each. |
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| unwords :: [String] -> String |
| unwords is an inverse operation to words.
It joins words with separating spaces. |
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| "Set" operations |
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| nub :: Eq a => [a] -> [a] |
| 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 equality test. |
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| delete :: Eq a => a -> [a] -> [a] |
delete x removes the first occurrence of x from its list argument.
For example,
delete 'a' "banana" == "bnana"
It is a special case of deleteBy, which allows the programmer to
supply their own equality test. |
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| (\\) :: Eq a => [a] -> [a] -> [a] |
The \\ function is list difference ((non-associative).
In the result of xs \\ ys, the first occurrence of each element of
ys in turn (if any) has been removed from xs. Thus
(xs ++ ys) \\ xs == ys.
It is a special case of deleteFirstsBy, which allows the programmer
to supply their own equality test. |
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| union :: Eq a => [a] -> [a] -> [a] |
The union function returns the list union of the two lists.
For example,
"dog" `union` "cow" == "dogcw"
Duplicates, and elements of the first list, are removed from the
the second list, but if the first list contains duplicates, so will
the result.
It is a special case of unionBy, which allows the programmer to supply
their own equality test. |
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| intersect :: Eq a => [a] -> [a] -> [a] |
The intersect function takes the list intersection of two lists.
For example,
[1,2,3,4] `intersect` [2,4,6,8] == [2,4]
If the first list contains duplicates, so will the result.
It is a special case of intersectBy, which allows the programmer to
supply their own equality test. |
|
| Ordered lists |
|
| sort :: Ord a => [a] -> [a] |
| The sort function implements a stable sorting algorithm.
It is a special case of sortBy, which allows the programmer to supply
their own comparison function. |
|
| insert :: Ord a => a -> [a] -> [a] |
| The insert function takes an element and a list and inserts the
element into the list at the last position where it is still less
than or equal to the next element. In particular, if the list
is sorted before the call, the result will also be sorted.
It is a special case of insertBy, which allows the programmer to
supply their own comparison function. |
|
| Generalized functions |
|
| The "By" operations |
|
| By convention, overloaded functions have a non-overloaded
counterpart whose name is suffixed with `By'. |
|
| User-supplied equality (replacing an Eq context) |
|
| The predicate is assumed to define an equivalence. |
|
| nubBy :: (a -> a -> Bool) -> [a] -> [a] |
| The nubBy function behaves just like nub, except it uses a
user-supplied equality predicate instead of the overloaded ==
function. |
|
| deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a] |
| The deleteBy function behaves like delete, but takes a
user-supplied equality predicate. |
|
| deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] |
| The deleteFirstsBy function takes a predicate and two lists and
returns the first list with the first occurrence of each element of
the second list removed. |
|
| unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] |
| The unionBy function is the non-overloaded version of union. |
|
| intersectBy :: (a -> a -> Bool) -> [a] -> [a] -> [a] |
| The intersectBy function is the non-overloaded version of intersect. |
|
| groupBy :: (a -> a -> Bool) -> [a] -> [[a]] |
| The groupBy function is the non-overloaded version of group. |
|
| User-supplied comparison (replacing an Ord context) |
|
| The function is assumed to define a total ordering. |
|
| sortBy :: (a -> a -> Ordering) -> [a] -> [a] |
| The sortBy function is the non-overloaded version of sort. |
|
| insertBy :: (a -> a -> Ordering) -> a -> [a] -> [a] |
| The non-overloaded version of insert. |
|
| maximumBy :: (a -> a -> Ordering) -> [a] -> a |
| The maximumBy function takes a comparison function and a list
and returns the greatest element of the list by the comparison function.
The list must be finite and non-empty. |
|
| minimumBy :: (a -> a -> Ordering) -> [a] -> a |
| The minimumBy function takes a comparison function and a list
and returns the least element of the list by the comparison function.
The list must be finite and non-empty. |
|
| The "generic" operations |
|
| The prefix `generic' indicates an overloaded function that
is a generalized version of a Prelude function. |
|
| genericLength :: Num i => [b] -> i |
| The genericLength function is an overloaded version of length. In
particular, instead of returning an Int, it returns any type which is
an instance of Num. It is, however, less efficient than length. |
|
| genericTake :: Integral i => i -> [a] -> [a] |
| The genericTake function is an overloaded version of take, which
accepts any Integral value as the number of elements to take. |
|
| genericDrop :: Integral i => i -> [a] -> [a] |
| The genericDrop function is an overloaded version of drop, which
accepts any Integral value as the number of elements to drop. |
|
| genericSplitAt :: Integral i => i -> [b] -> ([b], [b]) |
| The genericSplitAt function is an overloaded version of splitAt, which
accepts any Integral value as the position at which to split. |
|
| genericIndex :: Integral a => [b] -> a -> b |
| The genericIndex function is an overloaded version of !!, which
accepts any Integral value as the index. |
|
| genericReplicate :: Integral i => i -> a -> [a] |
| The genericReplicate function is an overloaded version of replicate,
which accepts any Integral value as the number of repetitions to make. |
|
| Produced by Haddock version 0.6 |
