Module BatList

module BatList: sig .. end

Additional and modified functions for lists.

The OCaml standard library provides a module for list functions. This BatList module can be used to extend the List module or as a standalone module. It provides new functions and modify the behavior of some other ones (in particular all functions are now tail-recursive).

The following functions have the same behavior as the List module ones but are tail-recursive: map, append, concat, flatten, fold_right, remove_assoc, remove_assq, split. That means they will not cause a Stack_overflow when used on very long list.

The implementation might be a little more slow in bytecode, but compiling in native code will not affect performances.

This module extends Stdlib's List module, go there for documentation on the rest of the functions and types.


List operations.

type 'a t = 'a list 

The type of lists

include BatEnum.Enumerable
include BatInterfaces.Mappable
Base operations
val is_empty : 'a list -> bool

is_empty e returns true if e does not contains any element.

val cons : 'a -> 'a list -> 'a list

cons h t returns the list starting with h and continuing as t.

val hd : 'a list -> 'a

Returns the first element of the list, or

val first : 'a list -> 'a

Alias to hd

val tl : 'a list -> 'a list

Return the given list without its first element.

val last : 'a list -> 'a

Returns the last element of the list, or

val length : 'a list -> int

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

val compare_lengths : 'a list -> 'b list -> int

Compare the lengths of two lists. compare_lengths l1 l2 is equivalent to compare (length l1) (length l2), except that the computation stops after itering on the shortest list.

val compare_length_with : 'a list -> int -> int

Compare the length of a list to an integer. compare_length_with l n is equivalent to compare (length l) n, except that the computation stops after at most n iterations on the list.

val at : 'a list -> int -> 'a

at l n returns the n-th element of the list l or

val at_opt : 'a list -> int -> 'a option

at_opt returns the n-th element of the list l or None if the index is beyond the length of l.

val rev : 'a list -> 'a list

List reversal.

val shuffle : ?state:Stdlib.Random.State.t -> 'a list -> 'a list

shuffle ~state:rs l randomly shuffles the elements of l. The optional random state rs allows to control the random numbers being used during shuffling (for reproducibility).

Shuffling is implemented using the Fisher-Yates algorithm on an array and works in O(n), where n is the number of elements of l.

val append : 'a list -> 'a list -> 'a list

append l1 l2 is a concatenation of l1 and l2. Same function as the infix operator @. Tail-recursive. This function takes O(length l1) time.

val rev_append : 'a list -> 'a list -> 'a list

List.rev_append l1 l2 reverses l1 and concatenates it to l2.

val concat : 'a list list -> 'a list

Concatenate a list of lists. The elements of the argument are all concatenated together (in the same order) to give the result. Tail-recursive.

val flatten : 'a list list -> 'a list

Same as concat.

val singleton : 'a -> 'a list

Create a list consisting of exactly one element.

Constructors
val make : int -> 'a -> 'a list

Similar to String.make, make n x returns a list containing n elements x.

val range : int -> [< `Downto | `To ] -> int -> int list

range 1 `To 3 = [1; 2; 3]. range 3 `Downto 1 = [3; 2; 1].

val frange : float -> [< `Downto | `To ] -> float -> int -> float list

frange start `To stop n generates (without accumulating floating point errors) n floats in the range [start..stop]. n must be >= 2. At each step, floats in an increasing (resp. decreasing) range increase (resp. decrease) by approximately (stop - start) / (n - 1).

val init : int -> (int -> 'a) -> 'a list

Similar to Array.init, init n f returns the list containing the results of (f 0),(f 1).... (f (n-1)).

val unfold : 'b -> ('b -> ('a * 'b) option) -> 'a list

unfold init f creates a list by repeatedly applying f to the second element of its own result, starting from the initial value init. The first element of each result is accumulated in a list. The list is terminated and returned as soon as f returns None.

Example: List.unfold 0 (fun x -> if x = 3 then None else Some (string_of_int x, x+1)) will return ["0";"1";"2"]

val unfold_exc : (unit -> 'a) -> 'a list * exn

Creates a list containing the results of sequential calls to f(). f() is called repeatedly until it throws an exception. Both the results list, as well as the exception thrown are returned in a (results_list, exn) pair. Warning: if calls to f() never throw an exception, unfold_exc is an infinite loop.

Iterators
val iter : ('a -> unit) -> 'a list -> unit

List.iter f [a0; a1; ...; an] applies function f in turn to a0; a1; ...; an. It is equivalent to begin f a0; f a1; ...; f an; () end.

val iteri : (int -> 'a -> unit) -> 'a list -> unit

iteri f l will call (f 0 a0); (f 1 a1) ... (f n an) where a0..an are the elements of the list l.

val map : ('a -> 'b) -> 'a list -> 'b list

map f [a0; a1; ...; an] applies function f to a0, a1, ..., an, and builds the list [f a0; f a1; ...; f an] with the results returned by f. Tail-recursive.

val rev_map : ('a -> 'b) -> 'a list -> 'b list

List.rev_map f l gives the same result as List.rev (List.map f l).

val mapi : (int -> 'a -> 'b) -> 'a list -> 'b list

mapi f l will build the list containing (f 0 a0); (f 1 a1) ... (f n an) where a0..an are the elements of the list l.

val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a

List.fold_left f a [b0; b1; ...; bn] is f (... (f (f a b0) b1) ...) bn.

val fold_lefti : ('a -> int -> 'b -> 'a) -> 'a -> 'b list -> 'a

As fold_left, but with the index of the element, from 0 to length li - 1, as additional argument.

val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b

List.fold_right f [a0; a1; ...; an] b is f a0 (f a1 (... (f an b) ...)). Tail-recursive.

val fold_righti : (int -> 'b -> 'a -> 'a) -> 'b list -> 'a -> 'a

As fold_right, but with the index of the element, from 0 to length li - 1, as additional argument.

val reduce : ('a -> 'a -> 'a) -> 'a list -> 'a

List.reduce f h::t is fold_left f h t.

val fold_left_map : ('a -> 'b -> 'a * 'c) -> 'a -> 'b list -> 'a * 'c list

Combines fold_left and map. Tail-recursive.

More precisely :

    fold_left_map f acc [] = (acc, [])

    fold_left_map f acc (x :: xs) =
      let (acc', y) = f acc x in
      let (res, ys) = fold_left_map acc' xs in
      (res, y :: ys)
    
val max : 'a list -> 'a

max l returns the largest value in l as judged by Pervasives.compare.

val min : 'a list -> 'a

min l returns the smallest value in l as judged by Pervasives.compare.

val sum : int list -> int

sum l returns the sum of the integers of l.

val fsum : float list -> float

fsum l returns the sum of the floats of l.

val favg : float list -> float

favg l returns the average of the floats of l

val kahan_sum : float list -> float

kahan_sum l returns a numerically-accurate sum of the floats of l. See BatArray.fsum for more details.

val min_max : ?cmp:('a -> 'a -> int) -> 'a list -> 'a * 'a

min_max l returns the pair (smallest, largest) from l as judged by Pervasives.compare (by default). You can provide another comparison function via the optional cmp parameter.

Iterators on two lists
val iter2 : ('a -> 'b -> unit) -> 'a list -> 'b list -> unit

List.iter2 f [a0; a1; ...; an] [b0; b1; ...; bn] calls in turn f a0 b0; f a1 b1; ...; f an bn.

val iter2i : (int -> 'a -> 'b -> unit) -> 'a list -> 'b list -> unit

List.iter2i f [a0; a1; ...; an] [b0; b1; ...; bn] calls in turn f 0 a0 b0; f 1 a1 b1; ...; f n an bn.

val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

List.map2 f [a0; a1; ...; an] [b0; b1; ...; bn] is [f a0 b0; f a1 b1; ...; f an bn].

val map2i : (int -> 'a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

List.map2i f [a0; a1; ...; an] [b0; b1; ...; bn] is [f 0 a0 b0; f 1 a1 b1; ...; f n an bn].

val rev_map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list

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.

val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> 'a

List.fold_left2 f a [b0; b1; ...; bn] [c0; c1; ...; cn] is f (... (f (f a b0 c0) b1 c1) ...) bn cn.

val fold_right2 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c

List.fold_right2 f [a0; a1; ...; an] [b0; b1; ...; bn] c is f a0 b0 (f a1 b1 (... (f an bn c) ...)).

List scanning
val mem : 'a -> 'a list -> bool

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

val mem_cmp : ('a -> 'a -> int) -> 'a -> 'a list -> bool

Same as List.mem, but the comparator function is explicitely provided.

val memq : 'a -> 'a list -> bool

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

Unary predicate, One list
val for_all : ('a -> bool) -> 'a list -> bool

for_all p [a0; a1; ...; an] checks if all elements of the list satisfy the predicate p. That is, it returns (p a0) && (p a1) && ... && (p an).

val exists : ('a -> bool) -> 'a list -> bool

exists p [a0; a1; ...; an] checks if at least one element of the list satisfies the predicate p. That is, it returns (p a0) || (p a1) || ... || (p an).

Binary predicate, Two lists
val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool

Same as List.for_all, but for a two-argument predicate.

val exists2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool

Same as List.exists, but for a two-argument predicate.

val subset : ('a -> 'b -> int) -> 'a list -> 'b list -> bool

subset cmp l l' check if all elements of the list l is contained in the list l' by applying cmp as comparator.

List searching
val find : ('a -> bool) -> 'a list -> 'a

find p l returns the first element of the list l that satisfies the predicate p.

val find_opt : ('a -> bool) -> 'a list -> 'a option

find_opt p l returns the first element of the list l that satisfies the predicate p, or None if there is no value that satisfies p in the list l.

val find_exn : ('a -> bool) -> exn -> 'a list -> 'a

find_exn p e l returns the first element of l such as p x returns true or raises e if such an element has not been found.

val findi : (int -> 'a -> bool) -> 'a list -> int * 'a

findi p e l returns the first element ai of l along with its index i such that p i ai is true, or

val find_map : ('a -> 'b option) -> 'a list -> 'b

find_map pred list finds the first element of list for which pred element returns Some r. It returns r immediately once found or

val rfind : ('a -> bool) -> 'a list -> 'a

rfind p l returns the last element x of l such as p x returns true or

val filter : ('a -> bool) -> 'a list -> 'a list

filter p l returns all the elements of the list l that satisfy the predicate p. The order of the elements in the input list is preserved.

val filteri : (int -> 'a -> bool) -> 'a list -> 'a list

filteri p [a0; a1; ...; an] returns all the elements ai of index i that satisfy the predicate p i ai. The order of the elements in the input list is preserved.

val filter_map : ('a -> 'b option) -> 'a list -> 'b list

filter_map f l calls (f a0) (f a1).... (f an) where a0,a1..an are the elements of l. It returns the list of elements bi such as f ai = Some bi (when f returns None, the corresponding element of l is discarded).

val filteri_map : (int -> 'a -> 'b option) -> 'a list -> 'b list

filteri_map f l calls (f 0 a0) (f 1 a1).... (f n an) where a0,a1..an are the elements of l. It returns the list of elements bi such as f ai = Some bi (when f returns None, the corresponding element of l is discarded).

val find_all : ('a -> bool) -> 'a list -> 'a list

find_all is another name for List.filter.

val partition : ('a -> bool) -> 'a list -> 'a list * 'a list

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.

val index_of : 'a -> 'a list -> int option

index_of e l returns the index of the first occurrence of e in l, or None if there is no occurrence of e in l

val index_ofq : 'a -> 'a list -> int option

index_ofq e l behaves as index_of e l except it uses physical equality

val rindex_of : 'a -> 'a list -> int option

rindex_of e l returns the index of the last occurrence of e in l, or None if there is no occurrence of e in l

val rindex_ofq : 'a -> 'a list -> int option

rindex_ofq e l behaves as rindex_of e l except it uses physical equality

val unique : ?eq:('a -> 'a -> bool) -> 'a list -> 'a list

unique cmp l returns the list l without any duplicate element. The default comparator ( = ) is used if no comparison function specified.

Implementation Note: The current implementation removes any elements where the tail of the list contains an equal element, thus it keeps the *last* copy of each equal element.

This function takes O(n^2) time.

val unique_cmp : ?cmp:('a -> 'a -> int) -> 'a list -> 'a list

As unique, except comparator parameter returns an int. Default comparator is Pervasives.compare. This function takes O(n log n) time.

Implementation Note: The current implementation removes subsequent elements that compare as equal to earlier elements in the list, thus it keeps the *first* copy of each equal element.

val unique_hash : ?hash:('a -> int) -> ?eq:('a -> 'a -> bool) -> 'a list -> 'a list

As unique, except uses a hash table to cut down the expected runtime to linear, assuming a good hash function. ?hash defaults to Hashtbl.hash and ?eq defaults to (=).

Implementation Note: The current implementation removes subsequent elements that hash and compare as equal to earlier elements in the list, thus it keeps the *first* copy of each equal element.

Association lists
val assoc : 'a -> ('a * 'b) list -> 'b

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.

val assoc_opt : 'a -> ('a * 'b) list -> 'b option

assoc_opt a l returns the value associated with key a in the list of pairs l. That is, assoc_opt a [ ...; (a,b); ...] = b if (a,b) is the leftmost binding of a in list l. Returns None if there is no value associated with a in the list l.

val assoc_inv : 'b -> ('a * 'b) list -> 'a

assoc_inv b l returns the key associated with value b in the list of pairs l. That is, assoc b [ ...; (a,b); ...] = a if (a,b) is the leftmost binding of a in list l.

val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list

remove_assoc a l returns the list of pairs l without the first pair with key a, if any. Tail-recursive.

val mem_assoc : 'a -> ('a * 'b) list -> bool

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

val assq : 'a -> ('a * 'b) list -> 'b

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

val assq_opt : 'a -> ('a * 'b) list -> 'b option

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

val assq_inv : 'b -> ('a * 'b) list -> 'a

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

val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list

Same as List.remove_assoc, but uses physical equality instead of structural equality to compare keys. Tail-recursive.

val mem_assq : 'a -> ('a * 'b) list -> bool

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

val modify : 'a -> ('b -> 'b) -> ('a * 'b) list -> ('a * 'b) list

modify a f l returns the same list as l but with value associated to key a replaced with f a.

val modify_def : 'b -> 'a -> ('b -> 'b) -> ('a * 'b) list -> ('a * 'b) list

modify_def dfl a f l performs as modify a f l except that it add an association from a to f dfl instead of raising Not_found.

val modify_opt : 'a -> ('b option -> 'b option) -> ('a * 'b) list -> ('a * 'b) list

modify_opt a f l allows to modify the binding for a in l or absence thereof.

List transformations
val modify_at : int -> ('a -> 'a) -> 'a list -> 'a list

modify_at n f l returns the same list as l but with nth-value a replaced with f a.

val modify_opt_at : int -> ('a -> 'a option) -> 'a list -> 'a list

modify_opt_at n f l returns the same list as l but with nth-value a removed if f a is None, and replaced by v if it is Some v.

val split_at : int -> 'a list -> 'a list * 'a list

split_at n l returns two lists l1 and l2, l1 containing the first n elements of l and l2 the others.

val split_nth : int -> 'a list -> 'a list * 'a list

Obsolete. As split_at.

val remove : 'a list -> 'a -> 'a list

remove l x returns the list l without the first element x found or returns l if no element is equal to x. Elements are compared using ( = ).

val remove_if : ('a -> bool) -> 'a list -> 'a list

remove_if cmp l is similar to remove, but with cmp used instead of ( = ).

val remove_at : int -> 'a list -> 'a list

remove_at i l returns the list l without the element at index i.

val remove_all : 'a list -> 'a -> 'a list

remove_all l x is similar to remove but removes all elements that are equal to x and not only the first one.

val take : int -> 'a list -> 'a list

take n l returns up to the n first elements from list l, if available.

val ntake : int -> 'a list -> 'a list list

ntake n l cuts l into lists of size at most n. n must be > 0.

val drop : int -> 'a list -> 'a list

drop n l returns l without the first n elements, or the empty list if l have less than n elements.

val takedrop : int -> 'a list -> 'a list * 'a list

takedrop n l is equivalent to (take n l, drop n l) but is done in one pass.

val take_while : ('a -> bool) -> 'a list -> 'a list

take_while p xs returns the (possibly empty) longest prefix of elements of xs that satisfy the predicate p.

val drop_while : ('a -> bool) -> 'a list -> 'a list

drop_while p xs returns the suffix remaining after take_while p xs.

val span : ('a -> bool) -> 'a list -> 'a list * 'a list

span, applied to a predicate p and a list xs, returns a tuple where first element is longest prefix (possibly empty) of xs of elements that satisfy p and second element is the remainder of the list. This is equivalent to (take_while p xs, drop_while p xs), but is done in one pass.

val nsplit : ('a -> bool) -> 'a list -> 'a list list

nsplit, applied to a predicate p and a list xs, returns a list of lists. xs is split when p x is true and x is excluded from the result.

If elements that satisfy p are consecutive, or at the beginning or end of the input list, the output list will contain empty lists marking their position. For example, split (fun n -> n<0) [-1;2;-2;-3;4;-5] is [[];[2];[];[4];[]]. This is consistent with the behavior of String.nsplit, where String.nsplit ";" "1;2;;3;" = ["1";"2";"";"3";""].

Note that for any xss : 'a list list and sep : 'a, we always have that flatten (interleave [sep] (nsplit ((=) sep) xss)) is xss.

val group_consecutive : ('a -> 'a -> bool) -> 'a list -> 'a list list

The group_consecutive 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_consecutive (=) [3;3;4;3;3] =  [[3;3];[4];[3;3]].

Note: In the next major version, this function is intended to replace the current group, which also sorts its input before grouping, and which will therefore be renamed into something more pertinent, such as classify, regroup, or group_sort.

val interleave : ?first:'a -> ?last:'a -> 'a -> 'a list -> 'a list

interleave ~first ~last sep [a0;a1;a2;...;an] returns first; a0; sep; a1; sep; a2; sep; ...; sep; an; last.

BatEnum functions

Abstraction layer.

val enum : 'a list -> 'a BatEnum.t

Returns an enumeration of the elements of a list. This enumeration may be used to visit elements of the list in forward order (i.e. from the first element to the last one).

val of_enum : 'a BatEnum.t -> 'a list

Build a list from an enumeration. In the result, elements appear in the same order as they did in the source enumeration.

val backwards : 'a list -> 'a BatEnum.t

Returns an enumeration of the elements of a list. This enumeration may be used to visit elements of the list in backwards order (i.e. from the last element to the first one).

val of_backwards : 'a BatEnum.t -> 'a list

Build a list from an enumeration. The first element of the enumeration becomes the last element of the list, the second element of the enumeration becomes the second-to-last element of the list...

List of pairs
val split : ('a * 'b) list -> 'a list * 'b list

Transform a list of pairs into a pair of lists: split [(a0,b0); (a1,b1); ...; (an,bn)] is ([a0; a1; ...; an], [b0;
    b1; ...; bn])
. Tail-recursive.

val combine : 'a list -> 'b list -> ('a * 'b) list

Transform a pair of lists into a list of pairs: combine [a0; a1; ...; an] [b0; b1; ...; bn] is [(a0,b0); (a1,b1); ...; (an,bn)].

Sorting
val sort : ('a -> 'a -> int) -> 'a list -> 'a list

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.

val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a list

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.

val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a list

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

val merge : ('a -> 'a -> int) -> 'a list -> 'a list -> 'a list

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).

val sort_uniq : ('a -> 'a -> int) -> 'a list -> 'a list

sort_uniq cmp l returns the list l sorted and without any duplicate element. cmp is a usual comparison function providing total order.

This function takes O(n log n) time.

val sort_unique : ('a -> 'a -> int) -> 'a list -> 'a list

synonym for sort_uniq

Utilities
val group : ('a -> 'a -> int) -> 'a list -> 'a list list

group cmp l returns list of groups and each group consists of elements judged equal by comparison function cmp. Groups in the resulting list appear in order given by cmp. All groups are always nonempty. group returns [] only if l is empty.

For example group cmp [f;c;b;e;d;a] can give [[a;b];[c];[d;e;f]] if following conditions are met: cmp a b = 0, cmp b c = -1, cmp c d = -1, cmp d e = 0, ...

See the note on group_consecutive.

val cartesian_product : 'a list -> 'b list -> ('a * 'b) list

Different from List.combine, this returns every pair of elements formed out of the two lists. cartesian_product [a0; a1; ...; an] [b0; b1; ...; bn] =
    [(a0,b0);(a0,b1); ...; (a0,bn); (a1,b0); ..; (a1, bn);
    ...; (an,bn)]
. The lists can be of unequal size.

val n_cartesian_product : 'a list list -> 'a list list

Given n lists, return the n-way cartesian product of these lists. Given [a;b];[c];[d;e;f], returns [a;c;d];[a;c;e];[a;c;f];[b;c;d];[b;c;e];[b;c;f], all ways of choosing one element from each input list.

val transpose : 'a list list -> 'a list list

Transposes a list of lists, turning rows of the input into columns of the output and vice versa.

Boilerplate code
Printing
val print : ?first:string ->
?last:string ->
?sep:string ->
('a BatInnerIO.output -> 'b -> unit) ->
'a BatInnerIO.output -> 'b list -> unit

Print the contents of a list

val eq : 'a BatOrd.eq -> 'a list BatOrd.eq
val ord : 'a BatOrd.ord -> 'a list BatOrd.ord
val compare : 'a BatOrd.comp -> 'a list BatOrd.comp

Comparison and equality for lists based on element comparison and equality

module Eq: 
functor (T : BatOrd.Eq-> Eq with type t = T.t list
module Ord: 
functor (T : BatOrd.Ord-> Ord with type t = T.t list
module Comp: 
functor (T : BatOrd.Comp-> Comp with type t = T.t list
Obsolete functions
val nth : 'a list -> int -> 'a

Obsolete. As at.

val nth_opt : 'a list -> int -> 'a option

Return the n-th element of the given list. The first element (head of the list) is at position 0. Return None if the list is too short. Raise Invalid_argument "List.nth" if n is negative.

val takewhile : ('a -> bool) -> 'a list -> 'a list

obsolete, as BatList.take_while

val dropwhile : ('a -> bool) -> 'a list -> 'a list

obsolete, as BatList.drop_while

Override modules

The following modules replace functions defined in List with functions behaving slightly differently but having the same name. This is by design: the functions are meant to override the corresponding functions of List.

module Exceptionless: sig .. end

Exceptionless counterparts for error-raising operations

module Infix: sig .. end

Infix submodule regrouping all infix operators

module Labels: sig .. end

Operations on List with labels.

val (@) : 'a list -> 'a list -> 'a list

Tail recursive List.append.