module BatDynArray:`sig`

..`end`

Dynamic arrays.

A dynamic array is equivalent to an OCaml array that will resize itself when elements are added or removed, except that floats are boxed and that no initialization element is required.

For all the traversal functions (iter, fold, map, etc.), what happens when the array that is being traversed is mutated is not defined.

**Author(s):**Brian Hurt, Nicolas Cannasse, David Teller (boilerplate code), andrepd

`type ``'a`

t

`include BatEnum.Enumerable`

`include BatInterfaces.Mappable`

`exception Invalid_arg of ``int * string * string`

When an operation on an array fails, `Invalid_arg`

is raised. The
integer is the value that made the operation fail, the first string
contains the function name that has been called and the second string
contains the parameter name that made the operation fail.

`val create : ``unit -> 'a t`

`create()`

returns a new empty dynamic array.

`val make : ``int -> 'a t`

`make count`

returns an array with some memory already allocated so
up to `count`

elements can be stored into it without resizing.

**Raises**`DynArray.Invalid_arg`

if make is called with a negative argument.

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

`init n f`

returns an array of `n`

elements filled with values
returned by `f 0 , f 1, ... f (n-1)`

.

**Raises**`DynArray.Invalid_arg`

if init is called with a negative argument.

`val singleton : ``'a -> 'a t`

Create an array consisting of exactly one element.

**Since**3.3.0

`val get : ``'a t -> int -> 'a`

`get darr idx`

gets the element in `darr`

at index `idx`

. If `darr`

has
`len`

elements in it, then the valid indexes range from `0`

to `len-1`

.

**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val set : ``'a t -> int -> 'a -> unit`

`set darr idx v`

sets the element of `darr`

at index `idx`

to value
`v`

. The previous value is overwritten.

**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val upd : ``'a t -> int -> ('a -> 'a) -> unit`

`upd darr idx f`

sets the element of `darr`

at index `idx`

to value
`f (get darr idx)`

). The previous value is overwritten.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val length : ``'a t -> int`

Return the number of elements in the array.

`val empty : ``'a t -> bool`

Return true if the number of elements in the array is 0.

`val first : ``'a t -> 'a`

`first darr`

returns the first element of `darr`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if length of the array is 0.

`val last : ``'a t -> 'a`

`last darr`

returns the last element of `darr`

.

**Raises**`DynArray.Invalid_arg`

if length of the array is 0.

`val left : ``'a t -> int -> 'a t`

`left r len`

returns the array containing the `len`

first characters of `r`

.
If `r`

contains less than `len`

characters, it returns `r`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val right : ``'a t -> int -> 'a t`

`right r len`

returns the array containing the `len`

last characters of `r`

.
If `r`

contains less than `len`

characters, it returns `r`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val head : ``'a t -> int -> 'a t`

Alias for `BatDynArray.left`

**Since**3.3.0

`val tail : ``'a t -> int -> 'a t`

`tail r pos`

returns the array containing all but the `pos`

first characters of `r`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val insert : ``'a t -> int -> 'a -> unit`

`insert darr idx v`

inserts `v`

into `darr`

at index `idx`

. All elements
of `darr`

with an index greater than or equal to `idx`

have their
index incremented (are moved up one place) to make room for the new
element.

**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val add : ``'a t -> 'a -> unit`

`add darr v`

appends `v`

onto the end of `darr`

. `v`

becomes the new
last element of `darr`

.

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

`append src dst`

adds all elements of `src`

to the end of `dst`

.

`val delete : ``'a t -> int -> unit`

`delete darr idx`

deletes the element of `darr`

at `idx`

. All elements
with an index greater than `idx`

have their index decremented (are
moved down one place) to fill in the hole.

**Raises**`DynArray.Invalid_arg`

if called with an invalid index.

`val delete_last : ``'a t -> unit`

`delete_last darr`

deletes the last element of `darr`

. This is equivalent
of doing `delete darr ((length darr) - 1)`

.

**Raises**`DynArray.Invalid_arg`

if length of the array is 0.

`val delete_range : ``'a t -> int -> int -> unit`

`delete_range darr idx len`

deletes `len`

elements starting at index `idx`

.
All elements with an index greater than `idx+len`

are moved to fill
in the hole.

**Raises**`DynArray.Invalid_arg`

if called with an invalid length or index.

`val clear : ``'a t -> unit`

remove all elements from the array and resize it to 0.

`val blit : ``'a t -> int -> 'a t -> int -> int -> unit`

`blit src srcidx dst dstidx len`

copies `len`

elements from `src`

starting with index `srcidx`

to `dst`

starting at `dstidx`

.

**Raises**`DynArray.Invalid_arg`

if called with an invalid length or indices.

`val compact : ``'a t -> unit`

`compact darr`

ensures that the space allocated by the array is minimal.

`val enum : ``'a t -> 'a BatEnum.t`

`enum darr`

returns the enumeration of `darr`

elements.

`val of_enum : ``'a BatEnum.t -> 'a t`

`of_enum e`

returns an array that holds, in order, the elements of `e`

.

`val range : ``'a t -> int BatEnum.t`

`range a`

returns an enumeration of all valid indices of the given
array, that is, `range a = 0 --^ ((length a) -1 )`

**Since**3.3.0

`val to_list : ``'a t -> 'a list`

`to_list darr`

returns the elements of `darr`

in order as a list.

`val of_list : ``'a list -> 'a t`

`of_list lst`

returns a dynamic array with the elements of `lst`

in
it in order.

`val to_array : ``'a t -> 'a array`

`to_array darr`

returns the elements of `darr`

in order as an array.

`val of_array : ``'a array -> 'a t`

`of_array arr`

returns an array with the elements of `arr`

in it
in order.

`val copy : ``'a t -> 'a t`

`copy a`

returns a fresh copy of `a`

, such that no modification of
`a`

affects the copy, or vice versa (all new memory is allocated for
the copy).

`val sub : ``'a t -> int -> int -> 'a t`

`sub a start len`

returns an array holding the subset of `len`

elements from `a`

starting with the element at index `idx`

.

**Raises**`DynArray.Invalid_arg`

if`start`

and`len`

do not designate a valid subarray of`a`

; that is, if`start < 0`

, or`len < 0`

, or`start + len > Array.length a`

.

`val fill : ``'a t -> int -> int -> 'a -> unit`

`fill a start len x`

modifies the array `a`

in place,
storing `x`

in elements number `start`

to `start + len - 1`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if`start`

and`len`

do not designate a valid subarray of`a`

.

`val split : ``('a * 'b) t -> 'a t * 'b t`

`split a`

converts the array of pairs `a`

into a pair of arrays.

**Since**3.3.0

`val combine : ``'a t -> 'b t -> ('a * 'b) t`

`combine a b`

converts arrays `[a0,...aN] [b0,...,bN]`

into
an array of pairs `[(a0,b0),...,(aN,bN)]`

.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val iter : ``('a -> unit) -> 'a t -> unit`

`iter f darr`

calls the function `f`

on every element of `darr`

. It
is equivalent to `for i = 0 to length darr - 1 do f (get darr i) done;`

`val iteri : ``(int -> 'a -> unit) -> 'a t -> unit`

`iteri f darr`

calls the function `f`

on every element of `darr`

. It
is equivalent to `for i = 0 to length darr - 1 do f i (get darr i) done;`

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

`map f darr`

applies the function `f`

to every element of `darr`

and creates a dynamic array from the results - similar to `List.map`

or
`Array.map`

.

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

`mapi f darr`

applies the function `f`

to every element of `darr`

and creates a dynamic array from the results - similar to `List.mapi`

or
`Array.mapi`

.

`val modify : ``('a -> 'a) -> 'a t -> unit`

`modify f a`

replaces every element `x`

of `a`

with `f x`

.

**Since**3.3.0

`val modifyi : ``(int -> 'a -> 'a) -> 'a t -> unit`

Same as `BatDynArray.modify`

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

**Since**3.3.0

`val fold_left : ``('a -> 'b -> 'a) -> 'a -> 'b t -> 'a`

`fold_left f x darr`

computes `f ( ... ( f ( f a0 x) a1) ) ... )`

, where

aN`a0,a1..aN`

are the indexed elements of `darr`

.

`val fold_right : ``('a -> 'b -> 'b) -> 'a t -> 'b -> 'b`

`fold_right f darr x`

computes ` f a0 (f a1 ( ... ( f aN x )`

, where

... ) ) `a0,a1..aN`

are the indexed elements of
`darr`

.

`val fold_lefti : ``('a -> int -> 'b -> 'a) -> 'a -> 'b t -> 'a`

As `fold_left`

, but with the index of the element as additional argument.

**Since**3.3.0

`val fold_righti : ``(int -> 'b -> 'a -> 'a) -> 'b t -> 'a -> 'a`

As `fold_right`

, but with the index of the element as additional argument.

**Since**3.3.0

`val reduce : ``('a -> 'a -> 'a) -> 'a t -> 'a`

`reduce f a`

is `fold_left f a0 [a1, ... aN]`

. This
is useful for merging a group of things that have no
reasonable default value to return if the group is empty.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

on empty arrays.

`val keep : ``('a -> bool) -> 'a t -> unit`

`keep p darr`

removes in place all the element `x`

of `darr`

such that `p x = false`

**Note** In previous versions, this function used to be called
`BatDynArray.filter`

. As this caused incompatibilities with comprehension
of dynamic arrays, the function name has been changed.

`val filter : ``('a -> bool) -> 'a t -> 'a t`

`filter p a`

returns all the elements of the array `a`

that satisfy the predicate `p`

. The order of the elements
in the input array is preserved.

**Note** This function replaces another function called `filter`

,
available in previous versions of the library. As the old function
was incompatible with comprehension of dynamic arrays, its name
was changed to `BatDynArray.keep`

.

`val find_all : ``('a -> bool) -> 'a t -> 'a t`

`find_all`

is another name for `filter`

.

**Since**3.3.0

`val filteri : ``(int -> 'a -> bool) -> 'a t -> 'a t`

As `filter`

but with the index passed to the predicate.

**Since**3.3.0

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

`filter_map f e`

returns an array consisting of all elements
`x`

such that `f y`

returns `Some x`

, where `y`

is an element
of `e`

.

`val partition : ``('a -> bool) -> 'a t -> 'a t * 'a t`

`partition p a`

returns a pair of arrays `(a1, a2)`

, where
`a1`

is the array of all the elements of `a`

that
satisfy the predicate `p`

, and `a2`

is the array of all the
elements of `a`

that do not satisfy `p`

.
The order of the elements in the input array is preserved.

**Since**3.3.0

`val for_all : ``('a -> bool) -> 'a t -> bool`

`for_all p [a0; a1; ...; an]`

checks if all elements of the
array satisfy the predicate `p`

. That is, it returns ` (p a0)`

.

&& (p a1) && ... && (p an)

**Since**3.3.0

`val exists : ``('a -> bool) -> 'a t -> bool`

`exists p [a0; a1; ...; an]`

checks if at least one element of
the array satisfies the predicate `p`

. That is, it returns `(p`

.

a0) || (p a1) || ... || (p an)

**Since**3.3.0

`val find : ``('a -> bool) -> 'a t -> 'a`

`find p a`

returns the first element of array `a`

that
satisfies the predicate `p`

.

**Since**3.3.0**Raises**`Not_found`

if there is no value that satisfies`p`

in the array`a`

.

`val findi : ``('a -> bool) -> 'a t -> int`

`findi p a`

returns the index of the first element of array `a`

that satisfies the predicate `p`

.

**Since**3.3.0**Raises**`Not_found`

if there is no value that satisfies`p`

in the array`a`

.

`val index_of : ``('a -> bool) -> 'a t -> int`

Alias for `BatDynArray.findi`

`val mem : ``'a -> 'a t -> bool`

`mem m a`

is true if and only if `m`

is equal to an element of `a`

.

**Since**3.3.0

`val memq : ``'a -> 'a t -> bool`

Same as `BatDynArray.mem`

but uses physical equality instead of
structural equality to compare array elements.

**Since**3.3.0

`val rev : ``'a t -> 'a t`

Array reversal.

**Since**3.3.0

`val rev_in_place : ``'a t -> unit`

In-place array reversal. The given array is updated.

**Since**3.3.0

`val max : ``'a t -> 'a`

`max a`

returns the largest value in `a`

as judged by
`Pervasives.compare`

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

on empty input.

`val min : ``'a t -> 'a`

`min a`

returns the smallest value in `a`

as judged by
`Pervasives.compare`

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

on empty input.

`val min_max : ``'a t -> 'a * 'a`

`min_max a`

returns the (smallest, largest) pair of values from `a`

as judged by `Pervasives.compare`

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

on empty input.

`val sum : ``int t -> int`

`sum l`

returns the sum of the integers of `l`

.

**Since**3.3.0

`val fsum : ``float t -> float`

`fsum l`

returns the sum of the floats of `l`

.

**Since**3.3.0

`val kahan_sum : ``float t -> float`

`kahan_sum l`

returns a numerically-accurate
sum of the floats of `l`

.

You should consider using Kahan summation when you really care about very small differences in the result, while the result or one of the intermediate sums can be very large (which usually results in loss of precision of floating-point addition).

The worst-case rounding error is constant, instead of growing with
(the square root of) the length of the input array as with `BatDynArray.fsum`

. On the other hand, processing each element requires four
floating-point operations instead of one. See
the wikipedia article on Kahan summation for more details.

**Since**3.3.0

`val avg : ``int t -> float`

`avg l`

returns the average of `l`

**Since**3.3.0

`val favg : ``float t -> float`

`favg l`

returns the average of `l`

**Since**3.3.0

`val iter2 : ``('a -> 'b -> unit) -> 'a t -> 'b t -> unit`

`iter2 f [a0, a1, ..., an] [b0, b1, ..., bn]`

performs calls `f a0 b0, f a1 b1, ..., f an bn`

in that order.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val iter2i : ``(int -> 'a -> 'b -> unit) -> 'a t -> 'b t -> unit`

`iter2i f [a0, a1, ..., an] [b0, b1, ..., bn]`

performs calls `f 0 a0 b0, f 1 a1 b1, ..., f n an bn`

in that
order.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val map2 : ``('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t`

As `BatDynArray.map`

but on two arrays.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val map2i : ``(int -> 'a -> 'b -> 'c) ->`

'a t -> 'b t -> 'c t

As `BatDynArray.mapi`

but on two arrays.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val for_all2 : ``('a -> 'b -> bool) -> 'a t -> 'b t -> bool`

As `BatDynArray.for_all`

but on two arrays.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val exists2 : ``('a -> 'b -> bool) -> 'a t -> 'b t -> bool`

As `BatDynArray.exists`

but on two arrays.

**Since**3.3.0**Raises**`DynArray.Invalid_arg`

if the two arrays have different lengths.

`val cartesian_product : ``'a t -> 'b t -> ('a * 'b) t`

Cartesian product of the two arrays.

**Since**3.3.0

type`resizer_t =`

`currslots:int -> oldlength:int -> newlength:int -> int`

The type of a resizer function.

Resizer functions are called whenever elements are added to or removed from the dynamic array to determine what the current number of storage spaces in the array should be. The three named arguments passed to a resizer are the current number of storage spaces in the array, the length of the array before the elements are added or removed, and the length the array will be after the elements are added or removed. If elements are being added, newlength will be larger than oldlength, if elements are being removed, newlength will be smaller than oldlength. If the resizer function returns exactly oldlength, the size of the array is only changed when adding an element while there is not enough space for it.

By default, all dynamic arrays are created with the `default_resizer`

.
When a dynamic array is created from another dynamic array (using `copy`

,
`map`

, etc. ) the resizer of the copy will be the same as the original
dynamic array resizer. To change the resizer, use the `set_resizer`

function.

`val set_resizer : ``'a t -> resizer_t -> unit`

Change the resizer for this array.

`val get_resizer : ``'a t -> resizer_t`

Get the current resizer function for a given array

`val default_resizer : ``resizer_t`

The default resizer function the library is using - in this version
of DynArray, this is the `exponential_resizer`

but should change in
next versions.

`val exponential_resizer : ``resizer_t`

The exponential resizer- The default resizer except when the resizer is being copied from some other darray.

`exponential_resizer`

works by doubling or halving the number of
slots until they "fit". If the number of slots is less than the
new length, the number of slots is doubled until it is greater
than the new length (or Sys.max_array_size is reached).

If the number of slots is more than four times the new length, the number of slots is halved until it is less than four times the new length.

Allowing darrays to fall below 25% utilization before shrinking them prevents "thrashing". Consider the case where the caller is constantly adding a few elements, and then removing a few elements, causing the length to constantly cross above and below a power of two. Shrinking the array when it falls below 50% would causing the underlying array to be constantly allocated and deallocated. A few elements would be added, causing the array to be reallocated and have a usage of just above 50%. Then a few elements would be remove, and the array would fall below 50% utilization and be reallocated yet again. The bulk of the array, untouched, would be copied and copied again. By setting the threshold at 25% instead, such "thrashing" only occurs with wild swings- adding and removing huge numbers of elements (more than half of the elements in the array).

`exponential_resizer`

is a good performing resizer for most
applications. A list allocates 2 words for every element, while an
array (with large numbers of elements) allocates only 1 word per
element (ignoring unboxed floats). On insert, `exponential_resizer`

keeps the amount of wasted "extra" array elements below 50%, meaning
that less than 2 words per element are used. Even on removals
where the amount of wasted space is allowed to rise to 75%, that
only means that darray is using 4 words per element. This is
generally not a significant overhead.

Furthermore, `exponential_resizer`

minimizes the number of copies
needed- appending n elements into an empty darray with initial size
0 requires between n and 2n elements of the array be copied- O(n)
work, or O(1) work per element (on average). A similar argument
can be made that deletes from the end of the array are O(1) as
well (obviously deletes from anywhere else are O(n) work- you
have to move the n or so elements above the deleted element down).

`val step_resizer : ``int -> resizer_t`

The stepwise resizer- another example of a resizer function, this time of a parameterized resizer.

The resizer returned by `step_resizer step`

returns the smallest
multiple of `step`

larger than `newlength`

if `currslots`

is less
then `newlength`

-`step`

or greater than `newlength`

.

For example, to make an darray with a step of 10, a length
of len, and a null of null, you would do:
`make`

~resizer:(`step_resizer`

10) len null

`val conservative_exponential_resizer : ``resizer_t`

`conservative_exponential_resizer`

is an example resizer function
which uses the oldlength parameter. It only shrinks the array
on inserts- no deletes shrink the array, only inserts. It does
this by comparing the oldlength and newlength parameters. Other
than that, it acts like `exponential_resizer`

.

`val create_with : ``resizer_t -> 'a t`

create a new dynamic array that uses the given resizer.

**Since**2.3.0

*

`val unsafe_get : ``'a t -> int -> 'a`

`val unsafe_set : ``'a t -> int -> 'a -> unit`

`val unsafe_upd : ``'a t -> int -> ('a -> 'a) -> unit`

**Since**3.3.0

Printing

`val print : ``?first:string ->`

?last:string ->

?sep:string ->

('a BatInnerIO.output -> 'b -> unit) ->

'a BatInnerIO.output -> 'b t -> unit

module Exceptionless:`sig`

..`end`

Operations on `DynArray`

without exceptions.