Module CCBV

Imperative Bitvectors.

A bitvector is stored in some form of internal array (on the heap). Is it a bit similar to a more storage-efficient version of bool CCVector.vector, with additional operations.

BREAKING CHANGES since 1.2: size is now stored along with the bitvector. Some functions have a new signature.

The size of the bitvector used to be rounded up to the multiple of 30 or 62. In other words some functions such as iter would iterate on more bits than what was originally asked for. This is not the case anymore.

type t

A resizable bitvector

val empty : unit -> t

Empty bitvector. Length is 0.

val create : size:int -> bool -> t

Create a bitvector of given size, with given default value. Length of result is size.

val init : int -> (int -> bool) -> t

init len f initializes a bitvector of length len, where bit i is true iff f i is.

  • since 3.9
val copy : t -> t

Copy of bitvector.

val cardinal : t -> int

Number of bits set to one, seen as a set of bits.

val length : t -> int

Size of underlying bitvector. This is not related to the underlying implementation. Changed at 1.2

val capacity : t -> int

The number of bits this bitvector can store without resizing.

  • since 1.2
val resize : t -> int -> unit

Resize the BV so that it has the specified length. This can grow the underlying array, but it will not shrink it, to minimize memory traffic.

  • raises Invalid_argument

    on negative sizes.

val resize_minimize_memory : t -> int -> unit

Same as resize, but this can also shrink the underlying array if this reduces the size.

  • raises Invalid_argument

    on negative sizes.

  • since 3.9
val is_empty : t -> bool

Are there any true bits?

val set : t -> int -> unit

Set i-th bit, extending the bitvector if needed.

val get : t -> int -> bool

Is the i-th bit true? Return false if the index is too high.

val reset : t -> int -> unit

Set i-th bit to 0, extending the bitvector if needed.

val set_bool : t -> int -> bool -> unit

Set or reset i-th bit.

  • since 3.9
val flip : t -> int -> unit

Flip i-th bit, extending the bitvector if needed.

val clear : t -> unit

Set every bit to 0. Does not change the length.

val clear_and_shrink : t -> unit

Set every bit to 0, and set length to 0.

  • since 3.9
val iter : t -> (int -> bool -> unit) -> unit

Iterate on all bits.

val iter_true : t -> (int -> unit) -> unit

Iterate on bits set to 1.

val to_list : t -> int list

List of indexes that are true.

val to_sorted_list : t -> int list

Same as to_list, but also guarantees the list is sorted in increasing order.

val of_list : int list -> t

From a list of true bits.

The bits are interpreted as indices into the returned bitvector, so the final bitvector bv will have length bv equal to 1 more than max of list indices.

val first : t -> int option

First set bit, or return None. Changed type at 1.2

val first_exn : t -> int

First set bit, or

  • raises Not_found

    if all bits are 0.

  • since 1.2
val filter : t -> (int -> bool) -> unit

filter bv p only keeps the true bits of bv whose index satisfies p index. Length is unchanged.

val negate_self : t -> unit

negate_self t flips all of the bits in t. Length is unchanged.

  • since 1.2
val negate : t -> t

negate t returns a copy of t with all of the bits flipped. Length is unchanged.

val union_into : into:t -> t -> unit

union_into ~into bv sets into to the union of itself and bv. Also updates the length of into to be at least length bv.

val inter_into : into:t -> t -> unit

inter_into ~into bv sets into to the intersection of itself and bv. Also updates the length of into to be at most length bv.

After executing:

  • length ~into' = min (length into) (length bv).
  • for all i: get into' ==> get into i /\ get bv i
val union : t -> t -> t

union bv1 bv2 returns the union of the two sets. The length of the result is the max of the inputs' lengths.

val inter : t -> t -> t

inter bv1 bv2 returns the intersection of the two sets. The length of the result is the min of the inputs' lengths.

val diff_into : into:t -> t -> unit

diff_into ~into t modifies into with only the bits set but not in t.

  • since 1.2
val diff : t -> t -> t

diff t1 t2 returns those bits found in t1 but not in t2.

  • since 1.2
val select : t -> 'a array -> 'a list

select arr bv selects the elements of arr whose index corresponds to a true bit in bv. If bv is too short, elements of arr with too high an index cannot be selected and are therefore not selected.

val selecti : t -> 'a array -> ('a * int) list

Same as select, but selected elements are paired with their indexes.

val equal : t -> t -> bool

Bitwise comparison, including the size (equal a b implies length a=length b).

  • since 3.5
type 'a iter = ('a -> unit) -> unit
val to_iter : t -> int iter

Iterate over the true bits.

val of_iter : int iter -> t

Build from true bits.

val pp : Stdlib.Format.formatter -> t -> unit

Print the bitvector as a string of bits.

  • since 0.13