Module `Nonstd.List`Source

include module type of struct include ListLabels end

Sourcetype 'a t = 'a list =

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

An alias for the type of lists.

Sourceval length : 'a list -> int

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

Sourceval 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

Sourceval 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

Sourceval cons : 'a -> 'a list -> 'a list

cons x xs is x :: xs

since 4.05.0

Sourceval 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

Sourceval rev : 'a list -> 'a list

List reversal.

Sourceval 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.

Sourceval 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).

Sourceval flatten : 'a list list -> 'a list

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

Comparison

Sourceval 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

Sourceval 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

Sourceval 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.

Source

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

Sourceval 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.

Sourceval 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.

Sourceval 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.

Source

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.

Source

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

Sourceval 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.

Sourceval 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.

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

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

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

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

List searching

Sourceval 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

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

find_all is another name for filter.

Sourceval 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

Sourceval 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

Sourceval 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

Sourceval 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.

Sourceval 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

Sourceval 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.

Sourceval 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.

Sourceval fast_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list

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

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

Same as sort, but also remove duplicates.

since 4.03.0

Lists and Sequences

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

Iterate on the list.

since 4.07

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

Create a list from a sequence.

since 4.07

Sourceval hd_exn : 'a list -> 'a

Sourceval hd : 'a t -> 'a option

Sourceval tl_exn : 'a list -> 'a list

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

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

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

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

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

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

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

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

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

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

changing the order of arguments on some standard List functions.

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

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

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

For the container interface.

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

Sourceval to_array : 'a list -> 'a array

Sourceval to_list : 'a -> 'a

Tail recursive versions of standard List module

Sourceval slow_append : 'a list -> 'a list -> 'a list

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

Sourceval append : 'a t -> 'a t -> 'a t

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Sourceval last : 'a t -> 'a option

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

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

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

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

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

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

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

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

Source

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

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

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

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

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

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

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

Sourcemodule Assoc : sig ... end

Sourceval assoc : [> `Use_sub_module ]

Sourceval assq : [> `Use_sub_module ]

Sourceval mem_assoc : [> `Use_sub_module ]

Sourceval mem_assq : [> `Use_sub_module ]

Sourceval remove_assoc : [> `Use_sub_module ]

Sourceval remove_assq : [> `Use_sub_module ]

package nonstd

Module Nonstd.ListSource

Comparison

Iterators

Iterators on two lists

List scanning

List searching

Association lists

Lists of pairs

Sorting

Lists and Sequences

Module `Nonstd.List`Source