Array utils (Labeled version of CCArray)
type 'a random_gen = Random.State.t -> 'atype 'a printer = Format.formatter -> 'a -> unitget 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) instead of get a n.
set a n x modifies array a in place, replacing element number n with x. You can also write a.(n) <- x instead of set a n x.
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.
create_float n returns a fresh float array of length n, with uninitialized data.
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 in order to the integers 0 to n-1.
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).
append v1 v2 returns a fresh array containing the concatenation of the arrays v1 and v2.
Same as append, but concatenates a list of arrays.
sub a ~pos ~len returns a fresh array of length len, containing the elements number pos to pos + len - 1 of array a.
copy a returns a copy of a, that is, a fresh array containing the same elements as a.
fill a ~pos ~len x modifies the array a in place, storing x in elements number pos to pos + len - 1.
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.
iter ~f a applies function f in turn to all the elements of a. It is equivalent to f a.(0); f a.(1); ...; f a.(length a - 1); ().
Same as iter, but the function is applied to the index of the element as first argument, and the element itself as second argument.
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); ...; f a.(length a - 1) |].
map_inplace ~f a applies function f to all elements of a, and updates their values in place.
Same as map, but the function is applied to the index of the element as first argument, and the element itself as second argument.
Same as map_inplace, but the function is applied to the index of the element as first argument, and the element itself as second argument.
fold_left ~f ~init a computes f (... (f (f init a.(0)) a.(1)) ...) a.(n-1), where n is the length of the array a.
fold_right ~f a ~init computes f a.(0) (f a.(1) ( ... (f a.(n-1) init) ...)), where n is the length of the array a.
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).
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).
Same as mem, but uses physical equality instead of structural equality to compare list elements.
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.
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.
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.
split [|(a1,b1); ...; (an,bn)|] is ([|a1; ...; an|], [|b1; ...; bn|]).
combine [|a1; ...; an|] [|b1; ...; bn|] is [|(a1,b1); ...; (an,bn)|]. Raise Invalid_argument if the two arrays have different lengths.
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, Stdlib.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 < 0cmp x y >= 0 and cmp y z >= 0 then cmp x z >= 0When 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 >= jSame as 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 sort.
Same as sort or stable_sort, whichever is faster on typical input.
val to_seqi : 'a array -> (int * 'a) Seq.tIterate on the array, in increasing order, yielding indices along elements. Modifications of the array during iteration will be reflected in the sequence.
val of_seq : 'a Seq.t -> 'a arrayCreate an array from the generator
Care must be taken when concurrently accessing arrays from multiple domains: accessing an array will never crash a program, but unsynchronized accesses might yield surprising (non-sequentially-consistent) results.
Every array operation that accesses more than one array element is not atomic. This includes iteration, scanning, sorting, splitting and combining arrays.
For example, consider the following program:
let size = 100_000_000
let a = ArrayLabels.make size 1
let d1 = Domain.spawn (fun () ->
ArrayLabels.iteri ~f:(fun i x -> a.(i) <- x + 1) a
)
let d2 = Domain.spawn (fun () ->
ArrayLabels.iteri ~f:(fun i x -> a.(i) <- 2 * x + 1) a
)
let () = Domain.join d1; Domain.join d2After executing this code, each field of the array a is either 2, 3, 4 or 5. If atomicity is required, then the user must implement their own synchronization (for example, using Mutex.t).
If two domains only access disjoint parts of the array, then the observed behaviour is the equivalent to some sequential interleaving of the operations from the two domains.
A data race is said to occur when two domains access the same array element without synchronization and at least one of the accesses is a write. In the absence of data races, the observed behaviour is equivalent to some sequential interleaving of the operations from different domains.
Whenever possible, data races should be avoided by using synchronization to mediate the accesses to the array elements.
Indeed, in the presence of data races, programs will not crash but the observed behaviour may not be equivalent to any sequential interleaving of operations from different domains. Nevertheless, even in the presence of data races, a read operation will return the value of some prior write to that location (with a few exceptions for float arrays).
Float arrays have two supplementary caveats in the presence of data races.
First, the blit operation might copy an array byte-by-byte. Data races between such a blit operation and another operation might produce surprising values due to tearing: partial writes interleaved with other operations can create float values that would not exist with a sequential execution.
For instance, at the end of
let zeros = Array.make size 0.
let max_floats = Array.make size Float.max_float
let res = Array.copy zeros
let d1 = Domain.spawn (fun () -> Array.blit zeros 0 res 0 size)
let d2 = Domain.spawn (fun () -> Array.blit max_floats 0 res 0 size)
let () = Domain.join d1; Domain.join d2the res array might contain values that are neither 0. nor max_float.
Second, on 32-bit architectures, getting or setting a field involves two separate memory accesses. In the presence of data races, the user may observe tearing on any operation.
val empty : 'a tempty is the empty array, physically equal to ||.
equal eq a1 a2 is true if the lengths of a1 and a2 are the same and if their corresponding elements test equal, using eq.
compare cmp a1 a2 compares arrays a1 and a2 using the function comparison cmp.
val swap : 'a t -> int -> int -> unitswap a i j swaps elements at indices i and j.
val get_safe : 'a t -> int -> 'a optionget_safe a i returns Some a.(i) if i is a valid index.
val fold : f:('a -> 'b -> 'a) -> init:'a -> 'b t -> 'afold ~f ~init a computes f (… (f (f init a.(0)) a.(1)) …) a.(n-1), where n is the length of the array a. Same as ArrayLabels.fold_left
val foldi : f:('a -> int -> 'b -> 'a) -> init:'a -> 'b t -> 'afoldi ~f ~init a is just like fold, but it also passes in the index of each element as the second argument to the folded function f.
val fold_while :
f:('a -> 'b -> 'a * [ `Stop | `Continue ]) ->
init:'a ->
'b t ->
'afold_while ~f ~init a folds left on array a until a stop condition via ('a, `Stop) is indicated by the accumulator.
fold_map ~f ~init a is a fold_left-like function, but it also maps the array to another array.
scan_left ~f ~init a returns the array [|init; f init x0; f (f init a.(0)) a.(1); …|] .
val reverse_in_place : 'a t -> unitreverse_in_place a reverses the array a in place.
val sorted : f:('a -> 'a -> int) -> 'a t -> 'a arraysorted ~f a makes a copy of a and sorts it with f.
val sort_indices : f:('a -> 'a -> int) -> 'a t -> int arraysort_indices ~f a returns a new array b, with the same length as a, such that b.(i) is the index at which the i-th element of sorted f a appears in a. a is not modified.
In other words, map (fun i -> a.(i)) (sort_indices f a) = sorted f a. sort_indices yields the inverse permutation of sort_ranking.
val sort_ranking : f:('a -> 'a -> int) -> 'a t -> int arraysort_ranking ~f a returns a new array b, with the same length as a, such that b.(i) is the index at which the i-th element of a appears in sorted f a. a is not modified.
In other words, map (fun i -> (sorted f a).(i)) (sort_ranking f a) = a. sort_ranking yields the inverse permutation of sort_indices.
In the absence of duplicate elements in a, we also have lookup_exn a.(i) (sorted a) = (sorted_ranking a).(i).
val mem : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> boolmem ~eq x a return true if x is present in a. Linear time.
val find_map : f:('a -> 'b option) -> 'a t -> 'b optionfind_map ~f a returns Some y if there is an element x such that f x = Some y. Otherwise returns None.
val find_map_i : f:(int -> 'a -> 'b option) -> 'a t -> 'b optionfind_map_i ~f a is like find_map, but the index of the element is also passed to the predicate function f.
val find_idx : f:('a -> bool) -> 'a t -> (int * 'a) optionfind_idx ~f a returns Some (i,x) where x is the i-th element of a, and f x holds. Otherwise returns None.
lookup ~cmp ~key a lookups the index of some key key in a sorted array a. Undefined behavior if the array a is not sorted wrt cmp. Complexity: O(log (n)) (dichotomic search).
val bsearch :
cmp:('a -> 'a -> int) ->
key:'a ->
'a t ->
[ `All_lower | `All_bigger | `Just_after of int | `Empty | `At of int ]bsearch ~cmp ~key a finds the index of the object key in the array a, provided a is sorted using cmp. If the array is not sorted, the result is not specified (may raise Invalid_argument).
Complexity: O(log n) where n is the length of the array a (dichotomic search).
for_all2 ~f [|a1; …; an|] [|b1; …; bn|] is true if each pair of elements ai bi satisfies the predicate f. That is, it returns (f a1 b1) && (f a2 b2) && … && (f an bn).
exists2 ~f [|a1; …; an|] [|b1; …; bn|] is true if any pair of elements ai bi satisfies the predicate f. That is, it returns (f a1 b1) || (f a2 b2) || … || (f an bn).
fold2 ~f ~init a b fold on two arrays a and b stepwise. It computes f (… (f init a1 b1) …) an bn.
iter2 ~f a b iterates on the two arrays a and b stepwise. It is equivalent to f a0 b0; …; f a.(length a - 1) b.(length b - 1); ().
val shuffle : 'a t -> unitshuffle a randomly shuffles the array a, in place.
val shuffle_with : Random.State.t -> 'a t -> unitshuffle_with rs a randomly shuffles the array a (like shuffle) but a specialized random state rs is used to control the random numbers being produced during shuffling (for reproducibility).
val random_choose : 'a t -> 'a random_genrandom_choose a rs randomly chooses an element of a.
to_string ~sep item_to_string a print a to a string using sep as a separator between elements of a.
to_iter a returns an iter of the elements of an array a. The input array a is shared with the sequence and modification of it will result in modification of the iterator.
to_seq a returns a Seq.t of the elements of an array a. The input array a is shared with the sequence and modification of it will result in modification of the sequence. Renamed from to_std_seq since 3.0.
val pp :
?pp_start:unit printer ->
?pp_stop:unit printer ->
?pp_sep:unit printer ->
'a printer ->
'a t printerpp ~pp_start ~pp_stop ~pp_sep pp_item ppf a formats the array a on ppf. Each element is formatted with pp_item, pp_start is called at the beginning, pp_stop is called at the end, pp_sep is called between each elements. By defaults pp_start and pp_stop does nothing and pp_sep defaults to (fun out -> Format.fprintf out ",@ ").
val pp_i :
?pp_start:unit printer ->
?pp_stop:unit printer ->
?pp_sep:unit printer ->
(int -> 'a printer) ->
'a t printerpp_i ~pp_start ~pp_stop ~pp_sep pp_item ppf a prints the array a on ppf. The printing function pp_item is giving both index and element. pp_start is called at the beginning, pp_stop is called at the end, pp_sep is called between each elements. By defaults pp_start and pp_stop does nothing and pp_sep defaults to (fun out -> Format.fprintf out ",@ ").
map2 ~f a b applies function f to all 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)|].
filter ~f a filters elements out of the array a. Only the elements satisfying the given predicate f will be kept.
filter_map ~f [|a1; …; an|] calls (f a1) … (f an) and returns an array b consisting of all elements bi such as f ai = Some bi. When f returns None, the corresponding element of a is discarded.
monoid_product ~f a b passes all combinaisons of tuples from the two arrays a and b to the function f.
flat_map ~f a transforms each element of a into an array, then flattens.
val except_idx : 'a t -> int -> 'a listexcept_idx a i removes the element of a at given index i, and returns the list of the other elements.
val random : 'a random_gen -> 'a t random_genval random_non_empty : 'a random_gen -> 'a t random_genval random_len : int -> 'a random_gen -> 'a t random_genmodule type MONO_ARRAY = sig ... endval sort_generic :
(module MONO_ARRAY with type elt = 'elt and type t = 'arr) ->
cmp:('elt -> 'elt -> int) ->
'arr ->
unitsort_generic (module M) ~cmp a sorts the array a, without allocating (eats stack space though). Performance might be lower than Array.sort.
It is convenient to openCCArray.Infix to access the infix operators without cluttering the scope too much.
module Infix : sig ... endinclude module type of Infixval (--) : int -> int -> int tx -- y creates an array containing integers in the range x .. y. Bounds included.
val (--^) : int -> int -> int tx --^ y creates an array containing integers in the range x .. y. Right bound excluded.
Let operators on OCaml >= 4.08.0, nothing otherwise