# struct BitArray

- BitArray
- Struct
- Value
- Object

## Overview

BitArray is an array data structure that compactly stores bits.

Bits externally represented as `Bool`s are stored internally as `UInt32`s. The total number of bits stored is set at creation and is immutable.

`BitArray` includes all the methods in `Enumerable`.

### Example

    require "bit_array"

    ba = BitArray.new(12) # => "BitArray[000000000000]"
    ba[2]                 # => false
    0.upto(5) { |i| ba[i * 2] = true }
    ba    # => "BitArray[101010101010]"
    ba[2] # => true

## Included Modules

- Indexable(Bool)

## Defined in:

## Constructors

- .new(size, initial : Bool = false)

  Creates a new `BitArray` of size bits.

## Instance Method Summary

- #==(other : BitArray)
- #==(other)
- #[](start : Int, count : Int)

  Returns count or less (if there aren't enough) elements starting at the given start index.

- #[](range : Range)

  Returns all elements that are within the given range.

- #[]=(index, value : Bool)

  Sets the bit at the given index.

- #hash(hasher)

  See `Object#hash(hasher)`

- #inspect(io : IO) : Nil

  Creates a string representation of self.

- #invert

  Inverts all bits in the array.

- #size : Int32

  The number of bits the BitArray stores

- #to_s(io : IO) : Nil

  Creates a string representation of self.

- #to_slice : Bytes

  Returns a `Bytes` able to read and write bytes from a buffer.

- #toggle(index)

  Toggles the bit at the given index.

- #unsafe_fetch(index : Int)

### Instance methods inherited from module `Indexable(Bool)`

[](index : Int) [], []?(index : Int) []?, bsearch(&block : T -> Bool) bsearch, bsearch_index(&block : T, Int32 -> Bool) bsearch_index, dig(index : Int, *subindexes) dig, dig?(index : Int, *subindexes) dig?, each(*, start : Int, count : Int, &block)
each(*, within range : Range, &block)
each(&block)
each each, each_index(*, start : Int, count : Int, &block)
each_index(&block) : Nil
each_index each_index, empty? empty?, equals?(other : Indexable, &block)
equals?(other, &block) equals?, fetch(index, default)
fetch(index : Int, &block) fetch, first
first(&block) first, first? first?, hash(hasher) hash, index(object, offset : Int = 0)
index(offset : Int = 0, &block) index, join(separator = "") join, last
last(&block) last, last? last?, reverse_each(&block) : Nil
reverse_each reverse_each, rindex(offset = size - 1, &block)
rindex(value, offset = size - 1) rindex, sample(random = Random::DEFAULT) sample, size size, to_a to_a, unsafe_fetch(index : Int) unsafe_fetch, values_at(*indexes : Int) values_at

### Instance methods inherited from module `Enumerable(Bool)`

all?(&block)
all?(pattern)
all? all?, any?(&block)
any?(pattern)
any? any?, chunks(&block : T -> U) forall U chunks, compact_map(&block) compact_map, count(item)
count(&block) count, cycle(&block)
cycle(n, &block) cycle, each(&block : T -> UNDERSCORE) each, each_cons(count : Int, reuse = false, &block) each_cons, each_slice(count : Int, reuse = false, &block) each_slice, each_with_index(offset = 0, &block) each_with_index, each_with_object(obj, &block) each_with_object, find(if_none = nil, &block) find, first(count : Int)
first first, first? first?, flat_map(&block : T -> Array(U) | Iterator(U) | U) forall U flat_map, grep(pattern) grep, group_by(&block : T -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &block) forall U in_groups_of, includes?(obj) includes?, index(&block)
index(obj) index, index_by(&block : T -> U) forall U index_by, join(separator = "", &block)
join(separator, io, &block)
join(separator, io)
join(separator = "") join, map(&block : T -> U) forall U map, map_with_index(&block : T, Int32 -> U) forall U map_with_index, max max, max? max?, max_by(&block : T -> U) forall U max_by, max_by?(&block : T -> U) forall U max_by?, max_of(&block : T -> U) forall U max_of, max_of?(&block : T -> U) forall U max_of?, min min, min? min?, min_by(&block : T -> U) forall U min_by, min_by?(&block : T -> U) forall U min_by?, min_of(&block : T -> U) forall U min_of, min_of?(&block : T -> U) forall U min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) forall U minmax_by, minmax_by?(&block : T -> U) forall U minmax_by?, minmax_of(&block : T -> U) forall U minmax_of, minmax_of?(&block : T -> U) forall U minmax_of?, none?
none?(pattern)
none?(&block) none?, one?(&block)
one?(pattern)
one? one?, partition(&block) partition, product(&block)
product(initial : Number, &block)
product
product(initial : Number) product, reduce(memo, &block)
reduce(&block) reduce, reduce?(&block) reduce?, reject(&block : T -> )
reject(type : U.class) forall U
reject(pattern) reject, select(pattern)
select(type : U.class) forall U
select(&block : T -> ) select, size size, skip(count : Int) skip, skip_while(&block) skip_while, sum(initial)
sum
sum(initial, &block)
sum(&block) sum, take_while(&block) take_while, tally : Hash(T, Int32) tally, to_a to_a, to_h
to_h(&block : T -> Tuple(K, V)) forall K, V to_h, to_set to_set, zip(*others : Indexable | Iterable | Iterator, &block)
zip(*others : Indexable | Iterable | Iterator) zip, zip?(*others : Indexable | Iterable | Iterator, &block)
zip?(*others : Indexable | Iterable | Iterator) zip?

### Instance methods inherited from module `Iterable(Bool)`

chunk(reuse = false, &block : T -> U) forall U chunk, chunk_while(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B chunk_while, cycle(n)
cycle cycle, each each, each_cons(count : Int, reuse = false) each_cons, each_slice(count : Int, reuse = false) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object, slice_after(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_after(pattern, reuse : Bool | Array(T) = false) slice_after, slice_before(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_before(pattern, reuse : Bool | Array(T) = false) slice_before, slice_when(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B slice_when

### Instance methods inherited from struct `Struct`

==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

### Instance methods inherited from struct `Value`

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, class class, dup dup, hash(hasher)
hash hash, inspect(io : IO) : Nil
inspect : String inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&block) tap, to_json(io : IO)
to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s : String
to_s(io : IO) : Nil to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&block) try, unsafe_as(type : T.class) forall T unsafe_as

### Constructor methods inherited from class `Object`

from_json(string_or_io, root : String) : self
from_json(string_or_io) : self from_json, from_yaml(string_or_io : String | IO) : self from_yaml

## Constructor Detail

def self.new(size, initial : Bool = false) #

Creates a new `BitArray` of size bits.

initial optionally sets the starting value, `true` or `false`, for all bits in the array.

## Instance Method Detail

def ==(other : BitArray) #
def ==(other) #
def [](start : Int, count : Int) #

Returns count or less (if there aren't enough) elements starting at the given start index.

Negative indices count backward from the end of the array (-1 is the last element). Additionally, an empty array is returned when the starting index for an element range is at the end of the array.

Raises `IndexError` if the starting index is out of range.

    require "bit_array"

    ba = BitArray.new(5)
    ba[0] = true; ba[2] = true; ba[4] = true
    ba # => BitArray[10101]

    ba[-3, 3] # => BitArray[101]
    ba[6, 1]  # raise indexError
    ba[1, 2]  # => BitArray[01]
    ba[5, 1]  # => BitArray[]

def [](range : Range) #

Returns all elements that are within the given range.

Negative indices count backward from the end of the array (-1 is the last element). Additionally, an empty array is returned when the starting index for an element range is at the end of the array.

Raises `IndexError` if the starting index is out of range.

    require "bit_array"

    ba = BitArray.new(5)
    ba[0] = true; ba[2] = true; ba[4] = true
    ba # => BitArray[10101]

    ba[1..3]    # => BitArray[010]
    ba[4..7]    # => BitArray[1]
    ba[6..10]   # raise IndexError
    ba[5..10]   # => BitArray[]
    ba[-2...-1] # => BitArray[0]

def []=(index, value : Bool) #

Sets the bit at the given index. Negative indices can be used to start counting from the end of the array. Raises `IndexError` if trying to access a bit outside the array's range.

    require "bit_array"

    ba = BitArray.new(5)
    ba[3] = true

def hash(hasher) #

See `Object#hash(hasher)`

def inspect(io : IO) : Nil #

Creates a string representation of self.

    require "bit_array"

    ba = BitArray.new(5)
    ba.to_s # => "BitArray[00000]"

def invert #

Inverts all bits in the array. Falses become `true` and vice versa.

    require "bit_array"

    ba = BitArray.new(5)
    ba[2] = true; ba[3] = true
    ba # => BitArray[00110]
    ba.invert
    ba # => BitArray[11001]

def size : Int32 #

The number of bits the BitArray stores

def to_s(io : IO) : Nil #

Creates a string representation of self.

    require "bit_array"

    ba = BitArray.new(5)
    ba.to_s # => "BitArray[00000]"

def to_slice : Bytes #

Returns a `Bytes` able to read and write bytes from a buffer. The slice will be long enough to hold all the bits groups in bytes despite the `UInt32` internal representation. It's useful for reading and writing a bit array from a byte buffer directly.

def toggle(index) #

Toggles the bit at the given index. A false bit becomes a `true` bit, and vice versa. Negative indices can be used to start counting from the end of the array. Raises `IndexError` if trying to access a bit outside the array's range.

    require "bit_array"

    ba = BitArray.new(5)
    ba[3] # => false
    ba.toggle(3)
    ba[3] # => true

def unsafe_fetch(index : Int) #