**Packages**- base

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.

The insert function takes an element and a list and inserts the element into the list at the last position 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.

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.

Return all the elements of a list except the last one. The list must be non-empty.

reverse xs returns the elements of xs in reverse order. xs must be finite.

Extract the elements after the head of a list, which must be non-empty.

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.

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.

A list producer that can be fused with foldr. This function is merely
> augment g xs = g (:) xs
but GHC's simplifier will transform an expression of the form foldr k z (augment g xs), which may arise after inlining, to g k (foldr k z xs), which avoids producing an intermediate list.

The sortWith function sorts a list of elements using the user supplied function to project something out of each element

scanl1 is a variant of scanl that has no starting value argument:
> scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]

The nubBy function behaves just like nub, except it uses a user-supplied equality predicate instead of the overloaded == function.

dropWhile p xs returns the suffix remaining after takeWhile p xs:
> dropWhile (< 3) [1,2,3,4,5,1,2,3] == [3,4,5,1,2,3]
> dropWhile (< 9) [1,2,3] == []
> dropWhile (< 0) [1,2,3] == [1,2,3]

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]

takeWhile, applied to a predicate p and a list xs, returns the longest prefix (possibly empty) of xs of elements that satisfy p:
> takeWhile (< 3) [1,2,3,4,1,2,3,4] == [1,2]
> takeWhile (< 9) [1,2,3] == [1,2,3]
> takeWhile (< 0) [1,2,3] == []

The genericDrop function is an overloaded version of drop, which accepts any Integral value as the number of elements to drop.

The genericTake function is an overloaded version of take, which accepts any Integral value as the number of elements to take.

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"

drop n xs returns the suffix of xs after the first n elements, or [] if n > length xs:
> drop 6 "Hello World!" == "World!"
> drop 3 [1,2,3,4,5] == [4,5]
> drop 3 [1,2] == []
> drop 3 [] == []
> drop (-1) [1,2] == [1,2]
> drop 0 [1,2] == [1,2]
It is an instance of the more general Data.List.genericDrop, in which n may be of any integral type.

take n, applied to a list xs, returns the prefix of xs of length n, or xs itself if n > length xs:
> take 5 "Hello World!" == "Hello"
> take 3 [1,2,3,4,5] == [1,2,3]
> take 3 [1,2] == [1,2]
> take 3 [] == []
> take (-1) [1,2] == []
> take 0 [1,2] == []
It is an instance of the more general Data.List.genericTake, in which n may be of any integral type.

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.

intercalate xs xss is equivalent to (concat (intersperse xs xss)). It inserts the list xs in between the lists in xss and concatenates the result.

The inits function returns all initial segments of the argument, shortest first. For example,
> inits "abc" == ["","a","ab","abc"]

The permutations function returns the list of all permutations of the argument.
> permutations "abc" == ["abc","bac","cba","bca","cab","acb"]

The subsequences function returns the list of all subsequences of the argument.
> subsequences "abc" == ["","a","b","ab","c","ac","bc","abc"]

The tails function returns all final segments of the argument, longest first. For example,
> tails "abc" == ["abc", "bc", "c",""]

List of elements of a structure.

Concatenate a list of lists.

The concatenation of all the elements of a container of lists.

The largest element of a non-empty structure.

The least element of a non-empty structure.

Extract the first element of a list, which must be non-empty.

Extract the last element of a list, which must be finite and non-empty.

repeat x is an infinite list, with x the value of every element.

The non-overloaded version of insert.

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.

The intersectBy function is the non-overloaded version of intersect.

Gets the module of a type constructor: take *.*.*... before name

Gets the unqualified type constructor: drop *.*.*... before name

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.

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.

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.
> [1,2,2,3,4] `intersect` [6,4,4,2] == [2,2,4]
It is a special case of intersectBy, which allows the programmer to supply their own equality test.

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.

The groupWith function uses the user supplied function which projects an element out of every list element in order to to first sort the input list and then to form groups by equality on these projected elements

This generalizes the list-based filter function.

Direct MonadPlus equivalent of filter filter = (mfilter:: (a -> Bool) -> [a] -> [a] applicable to any MonadPlus, for example mfilter odd (Just 1) == Just 1 mfilter odd (Just 2) == Nothing

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, ...]

Map a function over a list and concatenate the results.