Stdlib.Iarray(3)

🦋 Stdlib.Iarray 🦋

okay bestie, welcome to the Stdlib.Iarray page from the OCaml library manual — yes, the manual name is folded right in near the top, you're welcome ✨. This is all about immutable arrays, and they are lowkey iconic. 💅

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✨ NAME ✨

Stdlib.Iarray — no description. That's literally it. The page says “no description,” so I'm not inventing lore. 💀

🧚 Module 🧚

Module   Stdlib.Iarray

🌸 Documentation 🌸

Module Iarray
 : (module Stdlib__Iarray)

• type 'a t = 'a iarray — it's an alias for the type of immutable arrays, periodt.
• val length : 'a iarray -> int — returns the length (number of elements) of the given immutable array. slay.
• val get : 'a iarray -> int -> 'a — get a n returns the element number n of immutable array a. The first element has number 0. The last element has number length a - 1.

It raises Invalid_argument if n is outside the range 0 to (length a - 1).

• val init : int -> (int -> 'a) -> 'a iarray — init n f returns a fresh immutable array of length n, with element number i initialized to the result of f i. In other terms, init n f tabulates the results of f applied to the integers 0 to n-1.

It raises Invalid_argument if n < 0 or n > Sys.max_array_length. If the return type of f is float, then the maximum size is only Sys.max_array_length / 2.

• val append : 'a iarray -> 'a iarray -> 'a iarray — append v1 v2 returns a fresh immutable array containing the concatenation of the immutable arrays v1 and v2.

It raises Invalid_argument if length v1 + length v2 > Sys.max_array_length.

• val concat : 'a iarray list -> 'a iarray — same as Iarray.append, but concatenates a list of immutable arrays.
• val sub : 'a iarray -> pos:int -> len:int -> 'a iarray — sub a ~pos ~len returns a fresh immutable array of length len, containing the elements number pos to pos + len - 1 of immutable array a. This creates a copy of the selected portion of the immutable array.

It raises Invalid_argument if pos and len do not designate a valid subarray of a; that is, if pos < 0, or len < 0, or pos + len > length a.

• val to_list : 'a iarray -> 'a list — to_list a returns the list of all the elements of a.
• val of_list : 'a list -> 'a iarray — of_list l returns a fresh immutable array containing the elements of l.

It raises Invalid_argument if the length of l is greater than Sys.max_array_length.

🔄 Converting to and from mutable arrays 🔄

• val to_array : 'a iarray -> 'a array — to_array a returns a mutable copy of the immutable array a; that is, a fresh (mutable) array containing the same elements as a.
• val of_array : 'a array -> 'a iarray — of_array ma returns an immutable copy of the mutable array ma; that is, a fresh immutable array containing the same elements as ma.

⚖️ Comparison ⚖️

• val equal : ('a -> 'a -> bool) -> 'a iarray -> 'a iarray -> bool — eq [|a1; ...; an|] [|b1; ..; bm|] holds when the two input immutable arrays have the same length, and for each pair of elements ai, bi at the same position we have eq ai bi.
• val compare : ('a -> 'a -> int) -> 'a iarray -> 'a iarray -> int — provided the function cmp defines a preorder on elements, compare cmp a b compares first a and b by their length, and then, if equal, by their elements according to the lexicographic preorder.

For more details on comparison functions, see Iarray.sort.

🔁 Iterators 🔁

• val iter : ('a -> unit) -> 'a iarray -> unit — iter f a applies function f in turn to all the elements of a. It is equivalent to f (get a 0); f (get a 1); ...; f (get a (length a - 1)); ().
• val iteri : (int -> 'a -> unit) -> 'a iarray -> unit — same as Iarray.iter, but the function is applied to the index of the element as first argument, and the element itself as second argument.
• val map : ('a -> 'b) -> 'a iarray -> 'b iarray — map f a applies function f to all the elements of a, and builds an immutable array with the results returned by f: [| f (get a 0); f (get a 1); ...; f (get a (length a - 1)) |].
• val mapi : (int -> 'a -> 'b) -> 'a iarray -> 'b iarray — same as Iarray.map, but the function is applied to the index of the element as first argument, and the element itself as second argument.
• val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b iarray -> 'a — fold_left f init a computes f (... (f (f init (get a 0)) (get a 1)) ...) (get a n-1), where n is the length of the immutable array a.
• val fold_left_map : ('a -> 'b -> 'a * 'c) -> 'a -> 'b iarray -> 'a * 'c iarray — fold_left_map is a combination of Iarray.fold_left and Iarray.map that threads an accumulator through calls to f.
• val fold_right : ('b -> 'a -> 'a) -> 'b iarray -> 'a -> 'a — fold_right f a init computes f (get a 0) (f (get a 1) ( ... (f (get a (n-1)) init) ...)), where n is the length of the immutable array a.

👯 Iterators on two arrays 👯

• val iter2 : ('a -> 'b -> unit) -> 'a iarray -> 'b iarray -> unit — iter2 f a b applies function f to all the elements of a and b.

It raises Invalid_argument if the immutable arrays are not the same size.

• val map2 : ('a -> 'b -> 'c) -> 'a iarray -> 'b iarray -> 'c iarray — map2 f a b applies function f to all the elements of a and b, and builds an immutable array with the results returned by f:

[| f (get a 0) (get b 0);
      ...;
      f (get a (length a - 1)) (get b (length b - 1))|]

It raises Invalid_argument if the immutable arrays are not the same size.

🔎 Array scanning 🔎

• val for_all : ('a -> bool) -> 'a iarray -> bool — for_all f [|a1; ...; an|] checks if all elements of the immutable array satisfy the predicate f. That is, it returns (f a1) && (f a2) && ... && (f an).
• val exists : ('a -> bool) -> 'a iarray -> bool — exists f [|a1; ...; an|] checks if at least one element of the immutable array satisfies the predicate f. That is, it returns (f a1) || (f a2) || ... || (f an).
• val for_all2 : ('a -> 'b -> bool) -> 'a iarray -> 'b iarray -> bool — same as Iarray.for_all, but for a two-argument predicate.

It raises Invalid_argument if the two immutable arrays have different lengths.

• val exists2 : ('a -> 'b -> bool) -> 'a iarray -> 'b iarray -> bool — same as Iarray.exists, but for a two-argument predicate.

It raises Invalid_argument if the two immutable arrays have different lengths.

• val mem : 'a -> 'a iarray -> bool — mem a set is true if and only if a is structurally equal to an element of set (i.e. there is an x in set such that compare a x = 0).
• val memq : 'a -> 'a iarray -> bool — same as Iarray.mem, but uses physical equality instead of structural equality to compare array elements.
• val find_opt : ('a -> bool) -> 'a iarray -> 'a option — find_opt f a returns the first element of the immutable array a that satisfies the predicate f, or None if there is no value that satisfies f in the array a.
• val find_index : ('a -> bool) -> 'a iarray -> int option — find_index f a returns Some i, where i is the index of the first element of the array a that satisfies f x, if there is such an element.

It returns None if there is no such element.

• val find_map : ('a -> 'b option) -> 'a iarray -> 'b option — find_map f a applies f to the elements of a in order, and returns the first result of the form Some v, or None if none exist.
• val find_mapi : (int -> 'a -> 'b option) -> 'a iarray -> 'b option — same as find_map, but the predicate is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.

🎀 Arrays of pairs 🎀

• val split : ('a * 'b) iarray -> 'a iarray * 'b iarray — split [|(a1,b1); ...; (an,bn)|] is ([|a1; ...; an|], [|b1; ...; bn|]).
• val combine : 'a iarray -> 'b iarray -> ('a * 'b) iarray — combine [|a1; ...; an|] [|b1; ...; bn|] is [|(a1,b1); ...; (an,bn)|]. Raise Invalid_argument if the two immutable arrays have different lengths.

🧹 Sorting 🧹

• val sort : ('a -> 'a -> int) -> 'a iarray -> 'a iarray — sort an immutable array 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 below for a complete specification). For example, compare is a suitable comparison function. The result of calling sort is a fresh immutable array containing the same elements as the original sorted in increasing order. Other than this fresh array, sort is guaranteed to run in constant heap space and (at most) logarithmic stack space.

The current implementation uses Heap Sort. It runs in constant stack space.

Specification of the comparison function: Let a be the immutable array and cmp the comparison function. The following must be true for all x, y, z in a:

• cmp x y > 0 if and only if cmp y x < 0
• if cmp x y >= 0 and cmp y z >= 0 then cmp x z >= 0

The result of sort, which we'll call a', contains the same elements as a, reordered in such a way that for all i and j valid indices of a (or equivalently, of a'):

• cmp (get a' i) (get a' j) >= 0 if and only if i >= j

• val stable_sort : ('a -> 'a -> int) -> 'a iarray -> 'a iarray — same as Iarray.sort, but the sorting algorithm is stable (i.e. elements that compare equal are kept in their original order) and not guaranteed to run in constant heap space.

The current implementation uses Merge Sort. It uses a temporary array of length n/2, where n is the length of the immutable array. It is usually faster than the current implementation of Iarray.sort.

• val fast_sort : ('a -> 'a -> int) -> 'a iarray -> 'a iarray — same as Iarray.sort or Iarray.stable_sort, whichever is faster on typical input.

🔁 Iterators 🔁

• val to_seq : 'a iarray -> 'a Seq.t — iterate on the immutable array, in increasing order.
• val to_seqi : 'a iarray -> (int * 'a) Seq.t — iterate on the immutable array, in increasing order, yielding indices along elements.
• val of_seq : 'a Seq.t -> 'a iarray — create an immutable array from the generator.

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mwah 💋 this page was brought to you by OCamldoc, dated 2026-06-22, for Stdlib.Iarray(3) — bye bestie, go slay some immutable arrays! ✨🫶