# 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.

NOTE To use `BitArray`, you must explicitly import it with `require "bit_array"`

###
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::Mutable(Bool)

##
Defined in:

bit_array.cr

##
Constructors

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

  Creates a new `BitArray` of size bits.

- .new(size : Int, & : Int32 -> _)

  Creates a new `BitArray` of size bits and invokes the given block once for each index of `self`, setting the bit at that index to `true` if the block is truthy.

##
Instance Method Summary

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

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

- #[](range : Range) : BitArray

  Returns all elements that are within the given range.

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

  Sets the given value at the given index.

- #all? : Bool

  Returns `true` if all of the elements of the collection are truthy.

- #any? : Bool

  Returns `true` if at least one of the collection's members is truthy.

- #count(item : Bool) : Int32

  Returns the number of times that item is present in the bit array.

- #dup

  Returns a new `BitArray` with all of the same elements.

- #fill(value : Bool, start : Int, count : Int) : self

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

- #fill(value : Bool) : self

  Replaces every element in `self` with the given value.

- #hash(hasher)

  See `Object#hash(hasher)`

- #includes?(obj : Bool) : Bool

  Returns `true` if the collection contains obj, `false` otherwise.

- #index(obj : Bool, offset : Int = 0) : Int32 | Nil

  Returns the index of the first appearance of obj in `self` starting from the given offset, or `nil` if the value is not in `self`.

- #inspect(io : IO) : Nil

  Creates a string representation of `self`.

- #invert : Nil

  Inverts all bits in the array.

- #none? : Bool

  Returns `true` if all of the elements of the collection are falsey.

- #one? : Bool

  Returns `true` if only one element in this enumerable is truthy.

- #reverse! : self

  Reverses in-place all the elements of `self`.

- #rindex(obj : Bool, offset : Int = size - 1) : Int32 | Nil

  Returns the index of the last appearance of obj in `self`, or `nil` if obj is not in `self`.

- #rotate!(n : Int = 1) : self

  Shifts all elements of `self` to the left n times.

- #size : Int32

  The number of bits the BitArray stores

- #tally(hash)

  Tallies the collection.

- #tally : Hash(Bool, Int32)

  Tallies the collection.

- #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(start : Int, count : Int)

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

- #toggle(range : Range)

  Toggles all bits that are within the given range.

- #toggle(index) : Nil

  Toggles the bit at the given index.

- #unsafe_fetch(index : Int) : Bool

  Returns the element at the given index, without doing any bounds check.

- #unsafe_put(index : Int, value : Bool)

  Sets the element at the given index to value, without doing any bounds check.

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

[]=(index : Int, value : T) : T []=, fill(value : T, start : Int, count : Int) : self
fill(value : T, range : Range) : self
fill(value : T) : self
fill(start : Int, count : Int, & : Int32 -> T) : self
fill(range : Range, & : Int32 -> T) : self
fill(*, offset : Int = 0, & : Int32 -> T) : self fill, map!(& : T -> _) : self map!, map_with_index!(offset = 0, & : T, Int32 -> _) : self map_with_index!, reverse! : self reverse!, rotate!(n : Int = 1) : self rotate!, shuffle!(random : Random | Nil = nil) : self shuffle!, sort! : self
sort!(&block : T, T -> U) : self forall U sort!, sort_by!(&block : T -> _) : self sort_by!, swap(index0 : Int, index1 : Int) : self swap, unsafe_put(index : Int, value : T) unsafe_put, unstable_sort! : self
unstable_sort!(&block : T, T -> U) : self forall U unstable_sort!, unstable_sort_by!(&block : T -> _) : self unstable_sort_by!, update(index : Int, & : T -> _) : T update

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

[](index : Int) [], []?(index : Int) []?, bsearch(& : T -> _) bsearch, bsearch_index(& : T, Int32 -> _) bsearch_index, cartesian_product(*others : Indexable) cartesian_product, combinations(size : Int = self.size) combinations, dig(index : Int, *subindexes) dig, dig?(index : Int, *subindexes) dig?, each(& : T -> )
each
each(*, start : Int, count : Int, & : T -> )
each(*, within range : Range, & : T -> ) each, each_cartesian(*others : Indexable, &)
each_cartesian(*others : Indexable) each_cartesian, each_combination(size : Int = self.size, reuse = false, &) : Nil
each_combination(size : Int = self.size, reuse = false) each_combination, each_index(& : Int32 -> ) : Nil
each_index
each_index(*, start : Int, count : Int, &) each_index, each_permutation(size : Int = self.size, reuse = false, &) : Nil
each_permutation(size : Int = self.size, reuse = false) each_permutation, each_repeated_combination(size : Int = self.size, reuse = false, &) : Nil
each_repeated_combination(size : Int = self.size, reuse = false) each_repeated_combination, empty? : Bool empty?, equals?(other : Indexable, &) : Bool
equals?(other, &) equals?, fetch(index : Int, &)
fetch(index, default) fetch, find(if_none, _offset offset : Int, & : T -> )
find(if_none = nil, *, offset : Int, & : T -> ) find, find!(offset : Int = 0, & : T -> ) find!, first(&) first, hash(hasher) hash, index(object, offset : Int = 0)
index(offset : Int = 0, & : T -> ) index, index!(obj, offset : Int = 0)
index!(offset : Int = 0, & : T -> ) index!, join(separator : String | Char | Number = "") : String join, last : T
last(&) last, last? : T | Nil last?, permutations(size : Int = self.size) : Array(Array(T)) permutations, repeated_combinations(size : Int = self.size) : Array(Array(T)) repeated_combinations, reverse_each(& : T -> ) : Nil
reverse_each reverse_each, rindex(value, offset = size - 1)
rindex(offset = size - 1, & : T -> ) rindex, rindex!(value, offset = size - 1)
rindex!(offset = size - 1, & : T -> ) rindex!, sample(n : Int, random : Random | Nil = nil) : Array(T)
sample(random : Random | Nil = nil) sample, size size, to_a(& : T -> U) : Array(U) forall U to_a, unsafe_fetch(index : Int) unsafe_fetch, values_at(*indexes : Int) values_at

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

cartesian_product(indexables : Indexable(Indexable)) cartesian_product, each_cartesian(indexables : Indexable(Indexable), reuse = false, &)
each_cartesian(indexables : Indexable(Indexable), reuse = false) each_cartesian

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

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

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

element_type(x) element_type

### 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_cons_pair each_cons_pair, each_slice(count : Int, reuse = false) each_slice, each_step(n : Int)
each_step(n : Int, *, offset : Int) each_step, 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 : YAML::Any)
==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

### Class methods inherited from struct `Struct`

pre_initialize(address : Pointer) : Nil pre_initialize

### Instance methods inherited from struct `Value`

==(other : Log::Metadata::Value)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

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

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.new(size : Int, 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.

def self.new(size : Int, & : Int32 -> _) #

Creates a new `BitArray` of size bits and invokes the given block once for each index of `self`, setting the bit at that index to `true` if the block is truthy.

    BitArray.new(5) { |i| i >= 3 }     # => BitArray[00011]
    BitArray.new(6) { |i| i if i < 2 } # => BitArray[110000]

##
Instance Method Detail

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

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) : BitArray #

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 : Int, value : Bool) : Bool #

Sets the given value at the given index. Returns value.

Negative indices can be used to start counting from the end of the container. Raises `IndexError` if trying to set an element outside the container's range.

    ary = [1, 2, 3]
    ary[0] = 5
    ary # => [5, 2, 3]

    ary[3] = 5 # raises IndexError

def all? : Bool #

Returns `true` if all of the elements of the collection are truthy.

    [nil, true, 99].all? # => false
    [15].all?            # => true

def any? : Bool #

Returns `true` if at least one of the collection's members is truthy.

    [nil, true, 99].any? # => true
    [nil, false].any?    # => false
    ([] of Int32).any?   # => false

- `#present?` does not consider truthiness of elements.
- `#any?(&)` and `#any(pattern)` allow custom conditions.

NOTE `#any?` usually has the same semantics as `#present?`. They only differ if the element type can be falsey (i.e. `T <= Nil || T <= Pointer || T <= Bool`). It's typically advised to prefer `#present?` unless these specific truthiness semantics are required.

def count(item : Bool) : Int32 #

Returns the number of times that item is present in the bit array.

    ba = BitArray.new(12, true)
    ba[3] = false
    ba[7] = false
    ba.count(true)  # => 10
    ba.count(false) # => 2

def dup #

Returns a new `BitArray` with all of the same elements.

def fill(value : Bool, start : Int, count : Int) : self #

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

Negative values of start count from the end of the container.

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

Raises `ArgumentError` if count is negative.

    array = [1, 2, 3, 4, 5]
    array.fill(9, 2, 2) # => [1, 2, 9, 9, 5]
    array               # => [1, 2, 9, 9, 5]

def fill(value : Bool) : self #

Replaces every element in `self` with the given value. Returns `self`.

    array = [1, 2, 3, 4]
    array.fill(2) # => [2, 2, 2, 2]
    array         # => [2, 2, 2, 2]

def hash(hasher) #

See `Object#hash(hasher)`

def includes?(obj : Bool) : Bool #

Returns `true` if the collection contains obj, `false` otherwise.

    ba = BitArray.new(8, true)
    ba.includes?(true)  # => true
    ba.includes?(false) # => false

def index(obj : Bool, offset : Int = 0) : Int32 | Nil #

Returns the index of the first appearance of obj in `self` starting from the given offset, or `nil` if the value is not in `self`.

    ba = BitArray.new(16)
    ba[5] = ba[11] = true
    ba.index(true)             # => 5
    ba.index(true, offset: 8)  # => 11
    ba.index(true, offset: 12) # => nil

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 : Nil #

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 none? : Bool #

Returns `true` if all of the elements of the collection are falsey.

    [nil, false].none?       # => true
    [nil, false, true].none? # => false

It's the opposite of `#all?`.

def one? : Bool #

Returns `true` if only one element in this enumerable is truthy.

    [1, false, false].one? # => true
    [1, false, 3].one?     # => false
    [1].one?               # => true
    [false].one?           # => false

def reverse! : self #

Reverses in-place all the elements of `self`. Returns `self`.

def rindex(obj : Bool, offset : Int = size - 1) : Int32 | Nil #

Returns the index of the last appearance of obj in `self`, or `nil` if obj is not in `self`.

If offset is given, the search starts from that index towards the first elements in `self`.

    ba = BitArray.new(16)
    ba[5] = ba[11] = true
    ba.rindex(true)            # => 11
    ba.rindex(true, offset: 8) # => 5
    ba.rindex(true, offset: 4) # => nil

def rotate!(n : Int = 1) : self #

Shifts all elements of `self` to the left n times. Returns `self`.

    a1 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    a2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    a3 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

    a1.rotate!
    a2.rotate!(1)
    a3.rotate!(3)

    a1 # => [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
    a2 # => [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
    a3 # => [3, 4, 5, 6, 7, 8, 9, 0, 1, 2]

def size : Int32 #

The number of bits the BitArray stores

def tally(hash) #

Tallies the collection. Accepts a hash to count occurrences. The value corresponding to each element must be an integer. The number of occurrences is added to each value in hash, and hash is returned.

    hash = {} of Char => Int32
    words = ["crystal", "ruby"]
    words.each { |word| word.chars.tally(hash) }
    hash # => {'c' => 1, 'r' => 2, 'y' => 2, 's' => 1, 't' => 1, 'a' => 1, 'l' => 1, 'u' => 1, 'b' => 1}

def tally : Hash(Bool, Int32) #

Tallies the collection. Returns a hash where the keys are the elements and the values are numbers of elements in the collection that correspond to the key.

    ["a", "b", "c", "b"].tally # => {"a"=>1, "b"=>2, "c"=>1}

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.

WARNING It is undefined behaviour to set any of the unused bits of a bit array to `true` via a slice.

def toggle(start : Int, count : Int) #

Toggles count or less (if there aren't enough) bits starting at the given start index. A `false` bit becomes a `true` bit, and vice versa.

Negative indices count backward from the end of the array (-1 is the last element).

Raises `IndexError` if index is out of range. Raises `ArgumentError` if count is a negative number.

    require "bit_array"

    ba = BitArray.new(5)
    ba.to_s # => "BitArray[00000]"
    ba.toggle(1, 3)
    ba.to_s # => "BitArray[01110]"

def toggle(range : Range) #

Toggles all bits that are within the given range. A `false` bit becomes a `true` bit, and vice versa.

Negative indices count backward from the end of the array (-1 is the last element).

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

    require "bit_array"

    ba = BitArray.new(5)
    ba.to_s # => "BitArray[00000]"
    ba.toggle(1..-2)
    ba.to_s # => "BitArray[01110]"

def toggle(index) : Nil #

Toggles the bit at the given index. A `false` bit becomes a `true` bit, and vice versa.

Negative indices count backward from the end of the array (-1 is the last element).

Raises `IndexError` if index is out of range.

    require "bit_array"

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

def unsafe_fetch(index : Int) : Bool #
Description copied from module Indexable(Bool)

Returns the element at the given index, without doing any bounds check.

`Indexable` makes sure to invoke this method with index in `0...size`, so converting negative indices to positive ones is not needed here.

Clients never invoke this method directly. Instead, they access elements with `#[](index)` and `#[]?(index)`.

This method should only be directly invoked if you are absolutely sure the index is in bounds, to avoid a bounds check for a small boost of performance.

def unsafe_put(index : Int, value : Bool) #
Description copied from module Indexable::Mutable(Bool)

Sets the element at the given index to value, without doing any bounds check.

`Indexable::Mutable` makes sure to invoke this method with index in `0...size`, so converting negative indices to positive ones is not needed here.

Clients never invoke this method directly. Instead, they modify elements with `#[]=(index, value)`.

This method should only be directly invoked if you are absolutely sure the index is in bounds, to avoid a bounds check for a small boost of performance.