Stdlib.ArrayLabels(3) OCaml library Stdlib.ArrayLabels(3)

# [NAME](#NAME)

Stdlib.ArrayLabels - no description

# [Module](#Module)

Module Stdlib.ArrayLabels

# [Documentation](#Documentation)

Module **ArrayLabels**  
: **(module Stdlib\_\_ArrayLabels)**

*type* **'a** *t* = **'a array**

An alias for the type of arrays.

*val length* : **'a array -> int**

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

*val get* : **'a array -> int -> 'a**

**get a n** returns the element number **n** of array **a** . The first element has number 0. The last element has number **length a - 1** . You can also write [**a.(n)**](/man/enterprise-packages/ocaml-4/a..n) instead of **get a n** .

**Raises Invalid\_argument** if **n** is outside the range 0 to **(length a - 1)** .

*val set* : **'a array -> int -> 'a -> unit**

**set a n x** modifies array **a** in place, replacing element number **n** with **x** . You can also write **[a.(n)](/man/enterprise-packages/ocaml-4/a..n) <- x** instead of **set a n x** .

**Raises Invalid\_argument** if **n** is outside the range 0 to **length a - 1** .

*val make* : **int -> 'a -> 'a array**

**make n x** returns a fresh array of length **n** , initialized with **x** . All the elements of this new array are initially physically equal to **x** (in the sense of the **==** predicate). Consequently, if **x** is mutable, it is shared among all elements of the array, and modifying **x** through one of the array entries will modify all other entries at the same time.

**Raises Invalid\_argument** if **n < 0** or **n > Sys.max\_array\_length** . If the value of **x** is a floating-point number, then the maximum size is only **Sys.max\_array\_length / 2** .

*val create* : **int -> 'a -> 'a array**

**Deprecated.**

**create** is an alias for **ArrayLabels.make** .

*val create\_float* : **int -> float array**

**create\_float n** returns a fresh float array of length **n** , with uninitialized data.

**Since** 4.03

*val make\_float* : **int -> float array**

**Deprecated.**

**make\_float** is an alias for **ArrayLabels.create\_float** .

*val init* : **int -> f:(int -> 'a) -> 'a array**

**init n ~f** returns a fresh 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** .

**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 make\_matrix* : **dimx:int -> dimy:int -> 'a -> 'a array array**

**make\_matrix ~dimx ~dimy e** returns a two-dimensional array (an array of arrays) with first dimension **dimx** and second dimension **dimy** . All the elements of this new matrix are initially physically equal to **e** . The element ( **x,y** ) of a matrix **m** is accessed with the notation **m.(x).(y)** .

**Raises Invalid\_argument** if **dimx** or **dimy** is negative or greater than **Sys.max\_array\_length** . If the value of **e** is a floating-point number, then the maximum size is only **Sys.max\_array\_length / 2** .

*val create\_matrix* : **dimx:int -> dimy:int -> 'a -> 'a array array**

**Deprecated.**

**create\_matrix** is an alias for **ArrayLabels.make\_matrix** .

*val append* : **'a array -> 'a array -> 'a array**

**append v1 v2** returns a fresh array containing the concatenation of the arrays **v1** and **v2** .

**Raises Invalid\_argument** if **length v1 + length v2 > Sys.max\_array\_length** .

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

Same as **ArrayLabels.append** , but concatenates a list of arrays.

*val sub* : **'a array -> pos:int -> len:int -> 'a array**

**sub a ~pos ~len** returns a fresh array of length **len** , containing the elements number **pos** to **pos + len - 1** of array **a** .

**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 copy* : **'a array -> 'a array**

**copy a** returns a copy of **a** , that is, a fresh array containing the same elements as **a** .

*val fill* : **'a array -> pos:int -> len:int -> 'a -> unit**

**fill a ~pos ~len x** modifies the array **a** in place, storing **x** in elements number **pos** to **pos + len - 1** .

**Raises Invalid\_argument** if **pos** and **len** do not designate a valid subarray of **a** .

*val blit* : **src:'a array -> src\_pos:int -> dst:'a array -> dst\_pos:int -> len:int -> unit**

**blit ~src ~src\_pos ~dst ~dst\_pos ~len** copies **len** elements from array **src** , starting at element number **src\_pos** , to array **dst** , starting at element number **dst\_pos** . It works correctly even if **src** and **dst** are the same array, and the source and destination chunks overlap.

**Raises Invalid\_argument** if **src\_pos** and **len** do not designate a valid subarray of **src** , or if **dst\_pos** and **len** do not designate a valid subarray of **dst** .

*val to\_list* : **'a array -> 'a list**

**to\_list a** returns the list of all the elements of **a** .

*val of\_list* : **'a list -> 'a array**

**of\_list l** returns a fresh array containing the elements of **l** .

**Raises Invalid\_argument** if the length of **l** is greater than **Sys.max\_array\_length** .

## [Iterators](#Iterators)

*val iter* : **f:('a -> unit) -> 'a array -> unit**

**iter ~f a** applies function **f** in turn to all the elements of **a** . It is equivalent to **f a.(0); f [a.(1)](/man/enterprise-packages/ocaml-4/a..1); ...; f a.(length a - 1); ()** .

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

Same as **ArrayLabels.iter** , but the function is applied to the index of the element as first argument, and the element itself as second argument.

*val map* : **f:('a -> 'b) -> 'a array -> 'b array**

**map ~f a** applies function **f** to all the elements of **a** , and builds an array with the results returned by **f** : **\[| f a.(0); f [a.(1)](/man/enterprise-packages/ocaml-4/a..1); ...; f a.(length a - 1) |]** .

*val mapi* : **f:(int -> 'a -> 'b) -> 'a array -> 'b array**

Same as **ArrayLabels.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* : **f:('a -> 'b -> 'a) -> init:'a -> 'b array -> 'a**

**fold\_left ~f ~init a** computes **f (... (f (f init a.(0)) [a.(1)](/man/enterprise-packages/ocaml-4/a..1)) ...) a.(n-1)** , where **n** is the length of the array **a** .

*val fold\_left\_map* : **f:('a -> 'b -> 'a * 'c) -> init:'a -> 'b array -> 'a * 'c array**

**fold\_left\_map** is a combination of **ArrayLabels.fold\_left** and **ArrayLabels.map** that threads an accumulator through calls to **f** .

**Since** 4.13.0

*val fold\_right* : **f:('b -> 'a -> 'a) -> 'b array -> init:'a -> 'a**

**fold\_right ~f a ~init** computes **f a.(0) (f [a.(1)](/man/enterprise-packages/ocaml-4/a..1) ( ... (f a.(n-1) init) ...))** , where **n** is the length of the array **a** .

## [Iterators on two arrays](#Iterators_on_two_arrays)

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

**iter2 ~f a b** applies function **f** to all the elements of **a** and **b** .

**Since** 4.05.0

**Raises Invalid\_argument** if the arrays are not the same size.

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

**map2 ~f a b** applies function **f** to all the elements of **a** and **b** , and builds an array with the results returned by **f** : **\[| f a.(0) b.(0); ...; f a.(length a - 1) b.(length b - 1)|]** .

**Since** 4.05.0

**Raises Invalid\_argument** if the arrays are not the same size.

## [Array scanning](#Array_scanning)

*val for\_all* : **f:('a -> bool) -> 'a array -> bool**

**for\_all ~f \[|a1; ...; an|]** checks if all elements of the array satisfy the predicate **f** . That is, it returns **(f a1) && (f a2) && ... && (f an)** .

**Since** 4.03.0

*val exists* : **f:('a -> bool) -> 'a array -> bool**

**exists ~f \[|a1; ...; an|]** checks if at least one element of the array satisfies the predicate **f** . That is, it returns **(f a1) || (f a2) || ... || (f an)** .

**Since** 4.03.0

*val for\_all2* : **f:('a -> 'b -> bool) -> 'a array -> 'b array -> bool**

Same as **ArrayLabels.for\_all** , but for a two-argument predicate.

**Since** 4.11.0

**Raises Invalid\_argument** if the two arrays have different lengths.

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

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

**Since** 4.11.0

**Raises Invalid\_argument** if the two arrays have different lengths.

*val mem* : **'a -> set:'a array -> bool**

**mem a ~set** is true if and only if **a** is structurally equal to an element of **l** (i.e. there is an **x** in **l** such that **compare a x = 0** ).

**Since** 4.03.0

*val memq* : **'a -> set:'a array -> bool**

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

**Since** 4.03.0

*val find\_opt* : **f:('a -> bool) -> 'a array -> 'a option**

**find\_opt ~f a** returns the first element of the array **a** that satisfies the predicate **f** , or **None** if there is no value that satisfies **f** in the array **a** .

**Since** 4.13.0

*val find\_map* : **f:('a -> 'b option) -> 'a array -> '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.

**Since** 4.13.0

## [Arrays of pairs](#Arrays_of_pairs)

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

**split \[|(a1,b1); ...; (an,bn)|]** is **(\[|a1; ...; an|], \[|b1; ...; bn|])** .

**Since** 4.13.0

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

**combine \[|a1; ...; an|] \[|b1; ...; bn|]** is **\[|(a1,b1); ...; (an,bn)|]** . Raise **Invalid\_argument** if the two arrays have different lengths.

**Since** 4.13.0

## [Sorting](#Sorting)

*val sort* : **cmp:('a -> 'a -> int) -> 'a array -> unit**

Sort an 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. After calling **sort** , the array is sorted in place in increasing order. **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 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

When **sort** returns, **a** contains the same elements as before, reordered in such a way that for all i and j valid indices of **a** :

\- **cmp a.(i) a.(j)** >= 0 if and only if i >= j

*val stable\_sort* : **cmp:('a -> 'a -> int) -> 'a array -> unit**

Same as **ArrayLabels.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 array. It is usually faster than the current implementation of **ArrayLabels.sort** .

*val fast\_sort* : **cmp:('a -> 'a -> int) -> 'a array -> unit**

Same as **ArrayLabels.sort** or **ArrayLabels.stable\_sort** , whichever is faster on typical input.

## [Arrays and Sequences](#Arrays_and_Sequences)

*val to\_seq* : **'a array -> 'a Seq.t**

Iterate on the array, in increasing order. Modifications of the array during iteration will be reflected in the sequence.

**Since** 4.07

*val to\_seqi* : **'a array -> (int * 'a) Seq.t**

Iterate on the array, in increasing order, yielding indices along elements. Modifications of the array during iteration will be reflected in the sequence.

**Since** 4.07

*val of\_seq* : **'a Seq.t -> 'a array**

Create an array from the generator

**Since** 4.07

2026-10-27 OCamldoc

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Document: Stdlib.ArrayLabels(3o) from ocaml-4 4.14.4-r4 (Chainguard OS)
Source: https://github.com/ocaml/ocaml