nonstd 0.0.3 (latest) · OCaml Package

include module type of struct include ListLabels end

type 'a t = 'a list =

| []
| :: of 'a * 'a list

An alias for the type of lists.

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 reaching the end of the shortest list.

since 4.05.0

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

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

since 4.05.0

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

cons x xs is x :: xs

since 4.05.0

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.

raises Invalid_argument
if n is negative.

since 4.05

val rev : 'a list -> 'a list

List reversal.

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

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

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. Not tail-recursive (length of the argument + length of the longest sub-list).

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

Same as concat. Not tail-recursive (length of the argument + length of the longest sub-list).

Comparison

val equal : eq:('a -> 'a -> bool) -> 'a list -> 'a list -> bool

equal eq [a1; ...; an] [b1; ..; bm] holds when the two input lists have the same length, and for each pair of elements ai, bi at the same position we have eq ai bi.

Note: the eq function may be called even if the lists have different length. If you know your equality function is costly, you may want to check compare_lengths first.

since 4.12.0

val compare : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> int

compare cmp [a1; ...; an] [b1; ...; bm] performs a lexicographic comparison of the two input lists, using the same 'a -> 'a -> int interface as Stdlib.compare:

a1 :: l1 is smaller than a2 :: l2 (negative result) if a1 is smaller than a2, or if they are equal (0 result) and l1 is smaller than l2
the empty list [] is strictly smaller than non-empty lists

Note: the cmp function will be called even if the lists have different lengths.

since 4.12.0

Iterators

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

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

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

fold_left_map is a combination of fold_left and map that threads an accumulator through calls to f.

since 4.11.0

Iterators on two lists

val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit

iter2 ~f [a1; ...; an] [b1; ...; bn] calls in turn f a1 b1; ...; f an bn.

raises Invalid_argument
if the two lists are determined to have different lengths.

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

map2 ~f [a1; ...; an] [b1; ...; bn] is [f a1 b1; ...; f an bn].

raises Invalid_argument
if the two lists are determined to have different lengths. Not tail-recursive.

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

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

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

fold_left2 ~f ~init [a1; ...; an] [b1; ...; bn] is f (... (f (f init a1 b1) a2 b2) ...) an bn.

raises Invalid_argument
if the two lists are determined to have different lengths.

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

fold_right2 ~f [a1; ...; an] [b1; ...; bn] ~init is f a1 b1 (f a2 b2 (... (f an bn init) ...)).

raises Invalid_argument
if the two lists are determined to have different lengths. Not tail-recursive.

List scanning

val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool

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

raises Invalid_argument
if the two lists are determined to have different lengths.

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

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

raises Invalid_argument
if the two lists are determined to have different lengths.

val mem : 'a -> set:'a list -> bool

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

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

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

List searching

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

find ~f l returns the first element of the list l that satisfies the predicate f. Returns None if there is no value that satisfies f in the list l.

since 4.05

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

find_all is another name for filter.

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

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

Association lists

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); ...] = Some 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.

since 4.05

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

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

since 4.05.0

Lists of pairs

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

Transform a list of pairs into a pair of lists: split [(a1,b1); ...; (an,bn)] is ([a1; ...; an], [b1; ...; bn]). Not tail-recursive.

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

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

raises Invalid_argument
if the two lists have different lengths. Not tail-recursive.

Sorting

val sort : cmp:('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, Stdlib.compare is a suitable comparison function. The resulting list is sorted in increasing order. 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 : cmp:('a -> 'a -> int) -> 'a list -> 'a list

Same as 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 : cmp:('a -> 'a -> int) -> 'a list -> 'a list

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

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

Same as sort, but also remove duplicates.

since 4.03.0

Lists and Sequences

val to_seq : 'a list -> 'a Seq.t

Iterate on the list.

since 4.07

val of_seq : 'a Seq.t -> 'a list

Create a list from a sequence.

since 4.07

val hd_exn : 'a list -> 'a

val hd : 'a t -> 'a option

val tl_exn : 'a list -> 'a list

val tl : 'a t -> 'a list option

val nth : 'a t -> int -> 'a option

val nth_exn : 'a t -> int -> 'a

val rev_filter : 'a t -> f:('a -> bool) -> 'a t

val filter : 'a t -> f:('a -> bool) -> 'a list

val find_map : 'a t -> f:('a -> 'b option) -> 'b option

val find : 'a t -> f:('a -> bool) -> 'a option

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

val findi : 'a t -> f:(int -> 'a -> bool) -> (int * 'a) option

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

changing the order of arguments on some standard List functions.

val for_all : 'a list -> f:('a -> bool) -> bool

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

val fold : 'a list -> init:'b -> f:('b -> 'a -> 'b) -> 'b

For the container interface.

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

val to_array : 'a list -> 'a array

val to_list : 'a -> 'a

Tail recursive versions of standard List module

val slow_append : 'a list -> 'a list -> 'a list

val count_append : 'a t -> 'a t -> int -> 'a t

val append : 'a t -> 'a t -> 'a t

val map_slow : 'a list -> f:('a -> 'b) -> 'b list

val count_map : f:('a -> 'b) -> 'a t -> int -> 'b t

val map : 'a t -> f:('a -> 'b) -> 'b t

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

val rev_mapi : 'a t -> f:(int -> 'a -> 'b) -> i:int -> 'b t

val count_mapi : f:(int -> 'a -> 'b) -> 'a t -> int -> 'b t

val mapi : 'a t -> f:(int -> 'a -> 'b) -> 'b t

val map2_slow : 'a list -> 'b list -> f:('a -> 'b -> 'c) -> 'c list

val count_map2_exn : f:('a -> 'b -> 'c) -> 'a t -> 'b t -> int -> 'c t

val map2_exn : 'a t -> 'b t -> f:('a -> 'b -> 'c) -> 'c t

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

val foldi : 'a list -> f:(int -> 'b -> 'a -> 'b) -> init:'b -> 'b

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

val reduce : 'a t -> f:('a -> 'a -> 'a) -> 'a option

val concat_map : 'a t -> f:('a -> 'b list) -> 'b list

val concat_mapi : 'a t -> f:(int -> 'a -> 'b list) -> 'b list

val merge : 'a t -> 'a t -> cmp:('a -> 'a -> int) -> 'a list

val last : 'a t -> 'a option

val remove_consecutive_duplicates : 'a t -> equal:('a -> 'a -> bool) -> 'a list

val dedup : ?compare:('a -> 'a -> int) -> 'a list -> 'a list

val contains_dup : ?compare:('a -> 'a -> int) -> 'a list -> bool

val find_a_dup : ?compare:('a -> 'a -> int) -> 'a list -> 'a option

val init : int -> f:(int -> 'a) -> 'a t

val rev_filter_map : 'a t -> f:('a -> 'b option) -> 'b t

val filter_map : 'a t -> f:('a -> 'b option) -> 'b list

val filter_opt : 'a option t -> 'a list

val partition_map : 
  'a t ->
  f:('a -> [< `Fst of 'b | `Snd of 'c ]) ->
  'b list * 'c list

val split_n : 'a t -> int -> 'a t * 'a t

val take : 'a t -> int -> 'a t

val drop : 'a t -> int -> 'a t

val split_while : 'a t -> f:('a -> bool) -> 'a list * 'a t

val take_while : 'a t -> f:('a -> bool) -> 'a list

val drop_while : 'a t -> f:('a -> bool) -> 'a t

module Assoc : sig ... end

val assoc : [> `Use_sub_module ]

val assq : [> `Use_sub_module ]

val mem_assoc : [> `Use_sub_module ]

val mem_assq : [> `Use_sub_module ]

val remove_assoc : [> `Use_sub_module ]

val remove_assq : [> `Use_sub_module ]

package nonstd