package containers

Return the length (number of elements) of the given list.

Return the first element of the given list. Raise Failure "hd" if the list is empty.

Return the given list without its first element. Raise Failure "tl" if the list is empty.

Return the n-th element of the given list. The first element (head of the list) is at position 0. Raise Failure "nth" if the list is too short. Raise Invalid_argument "List.nth" if n is negative.

List reversal.

List.rev_append l1 l2 reverses l1 and concatenates it to l2. This is equivalent to List.rev l1 @ l2, but rev_append is tail-recursive and more efficient.

Concatenate a list of lists. The elements of the argument are all concatenated together (in the same order) to give the result. Not tail-recursive (length of the argument + length of the longest sub-list).

List.iter f [a1; ...; an] applies function f in turn to a1; ...; an. It is equivalent to begin f a1; f a2; ...; f an; () end.

Same as List.iter, but the function is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.

• since 4.00.0

Same as List.map, but the function is applied to the index of the element as first argument (counting from 0), and the element itself as second argument. Not tail-recursive.

• since 4.00.0

List.rev_map f l gives the same result as List.rev (List.map f l), but is tail-recursive and more efficient.

List.fold_left f a [b1; ...; bn] is f (... (f (f a b1) b2) ...) bn.

List.iter2 f [a1; ...; an] [b1; ...; bn] calls in turn f a1 b1; ...; f an bn. Raise Invalid_argument if the two lists are determined to have different lengths.

List.map2 f [a1; ...; an] [b1; ...; bn] is [f a1 b1; ...; f an bn]. Raise Invalid_argument if the two lists are determined to have different lengths. Not tail-recursive.

List.rev_map2 f l1 l2 gives the same result as List.rev (List.map2 f l1 l2), but is tail-recursive and more efficient.

List.fold_left2 f a [b1; ...; bn] [c1; ...; cn] is f (... (f (f a b1 c1) b2 c2) ...) bn cn. Raise Invalid_argument if the two lists are determined to have different lengths.

List.fold_right2 f [a1; ...; an] [b1; ...; bn] c is f a1 b1 (f a2 b2 (... (f an bn c) ...)). Raise Invalid_argument if the two lists are determined to have different lengths. Not tail-recursive.

for_all p [a1; ...; an] checks if all elements of the list satisfy the predicate p. That is, it returns (p a1) && (p a2) && ... && (p an).

exists p [a1; ...; an] checks if at least one element of the list satisfies the predicate p. That is, it returns (p a1) || (p a2) || ... || (p an).

Same as List.for_all, but for a two-argument predicate. Raise Invalid_argument if the two lists are determined to have different lengths.

Same as List.exists, but for a two-argument predicate. Raise Invalid_argument if the two lists are determined to have different lengths.

mem a l is true if and only if a is equal to an element of l.

Same as List.mem, but uses physical equality instead of structural equality to compare list elements.

find_all is another name for List.filter.

partition p l returns a pair of lists (l1, l2), where l1 is the list of all the elements of l that satisfy the predicate p, and l2 is the list of all the elements of l that do not satisfy p. The order of the elements in the input list is preserved.

assoc a l returns the value associated with key a in the list of pairs l. That is, assoc a [ ...; (a,b); ...] = b if (a,b) is the leftmost binding of a in list l. Raise Not_found if there is no value associated with a in the list l.

Same as List.assoc, but uses physical equality instead of structural equality to compare keys.

Same as List.assoc, but simply return true if a binding exists, and false if no bindings exist for the given key.

Same as List.mem_assoc, but uses physical equality instead of structural equality to compare keys.

remove_assoc a l returns the list of pairs l without the first pair with key a, if any. Not tail-recursive.

Same as List.remove_assoc, but uses physical equality instead of structural equality to compare keys. Not tail-recursive.

Transform a pair of lists into a list of pairs: combine [a1; ...; an] [b1; ...; bn] is [(a1,b1); ...; (an,bn)]. Raise Invalid_argument if the two lists have different lengths. Not tail-recursive.

Sort a list in increasing order according to a comparison function. The comparison function must return 0 if its arguments compare as equal, a positive integer if the first is greater, and a negative integer if the first is smaller (see Array.sort for a complete specification). For example, Pervasives.compare is a suitable comparison function. The resulting list is sorted in increasing order. List.sort is guaranteed to run in constant heap space (in addition to the size of the result list) and logarithmic stack space.

The current implementation uses Merge Sort. It runs in constant heap space and logarithmic stack space.

Same as List.sort, but the sorting algorithm is guaranteed to be stable (i.e. elements that compare equal are kept in their original order) .

The current implementation uses Merge Sort. It runs in constant heap space and logarithmic stack space.

Same as List.sort or List.stable_sort, whichever is faster on typical input.

Merge two lists: Assuming that l1 and l2 are sorted according to the comparison function cmp, merge cmp l1 l2 will return a sorted list containting all the elements of l1 and l2. If several elements compare equal, the elements of l1 will be before the elements of l2. Not tail-recursive (sum of the lengths of the arguments).

is_empty l returns true iff l = []

• since 0.11

Safe version of map

Infix version of map with reversed arguments

• since 0.5

cons x l is x::l

• since 0.12

Safe version of append

Safe version of List.filter

Safe version of fold_right

Fold until a stop condition via ('a, `Stop) is indicated by the accumulator

• since 0.8

Similar to Array.init

• since 0.6

map and flatten at the same time (safe). Evaluation order is not guaranteed.

Safe flatten

cartesian product of the two lists, with the given combinator

Fold on the cartesian product

All pairs of distinct positions of the list. list_diagonal l will return the list of List.nth i l, List.nth j l if i < j.

partition_map f l maps f on l and gather results in lists:

• if f x = `Left y, adds y to the first list
• if f x = `Right z, adds z to the second list
• if f x = `Drop, ignores x

• since 0.11

take the n first elements, drop the rest

drop the n first elements, keep the rest

split n l returns l1, l2 such that l1 @ l2 = l and length l1 = min (length l) n

last n l takes the last n elements of l (or less if l doesn't have that many elements

find_pred p l finds the first element of l that satisfies p, or returns None if no element satisfies p

• since 0.11

Unsafe version of find_pred

• raises Not_found

  if no such element is found

• since 0.11

find f l traverses l, applying f to each element. If for some element x, f x = Some y, then Some y is returned. Otherwise the call returns None

• since 0.11

• deprecated

  in favor of find_map, for the name is too confusing

Like find_map, but also pass the index to the predicate function.

• since 0.11

• deprecated

  in favor of find_mapi, name is too confusing

• since 0.3.4

find p x returns Some (i,x) where x is the i-th element of l, and p x holds. Otherwise returns None

remove ~x l removes every instance of x from l. Tailrec.

• parameter eq

  equality function

• since 0.11

Map and remove elements at the same time

merges elements from both sorted list

Sort the list and remove duplicate elements

sorted_merge_uniq l1 l2 merges the sorted lists l1 and l2 and removes duplicates

• since 0.10

uniq_succ l removes duplicate elements that occur one next to the other. Examples: uniq_succ [1;2;1] = [1;2;1] uniq_succ [1;1;2] = [1;2]

• since 0.10

group_succ ~eq l groups together consecutive elements that are equal according to eq

• since 0.11

range i j iterates on integers from i to j included . It works both for decreasing and increasing ranges

Same as range but the second bound is excluded. For instance range' 0 5 = [0;1;2;3;4]

Infix alias for range

replicate the given element n times

concatenate the list with itself n times

Randomly choose an element in the list.

• raises Not_found

  if the list is empty