NAME¶

std::vector - std::vector

Synopsis¶

Defined in header <vector>
template<class Allocator>
class vector<bool, Allocator>;

std::vector<bool> is a possibly space-efficient specialization of std::vector for
the type bool.

The manner in which std::vector<bool> is made space efficient (as well as whether it
is optimized at all) is implementation defined. One potential optimization involves
coalescing vector elements such that each element occupies a single bit instead of
sizeof(bool) bytes.

std::vector<bool> behaves similarly to std::vector, but in order to be space
efficient, it:

* Does not necessarily store its elements as a contiguous array.
* Exposes class std::vector<bool>::reference as a method of accessing individual
bits. In particular, objects of this class are returned by operator[] by value.
* Does not use std::allocator_traits::construct to construct bit values.
* Does not guarantee that different elements in the same container can be modified
concurrently by different threads.

Member types¶

Member type Definition
value_type bool
allocator_type Allocator
size_type implementation-defined
difference_type implementation-defined
reference proxy class representing a reference to a single bool
(class)
const_reference bool
pointer implementation-defined
const_pointer implementation-defined
iterator implementation-defined (until C++20)
implementation-defined ConstexprIterator (since C++20)
const_iterator implementation-defined (until C++20)
implementation-defined ConstexprIterator (since C++20)
reverse_iterator std::reverse_iterator<iterator>
const_reverse_iterator std::reverse_iterator<const_iterator>

Member functions¶

constructor constructs the vector
(public member function of std::vector<T,Allocator>)
destructor destructs the vector
(public member function of std::vector<T,Allocator>)
operator= assigns values to the container
(public member function of std::vector<T,Allocator>)
assign assigns values to the container
(public member function of std::vector<T,Allocator>)
get_allocator returns the associated allocator
(public member function of std::vector<T,Allocator>)

Element access¶

at access specified element with bounds checking
(public member function of std::vector<T,Allocator>)
operator[] access specified element
(public member function of std::vector<T,Allocator>)
front access the first element
(public member function of std::vector<T,Allocator>)
back access the last element
(public member function of std::vector<T,Allocator>)

Iterators¶

begin returns an iterator to the beginning
cbegin (public member function of std::vector<T,Allocator>)
(C++11)
end returns an iterator to the end
cend (public member function of std::vector<T,Allocator>)
(C++11)
rbegin returns a reverse iterator to the beginning
crbegin (public member function of std::vector<T,Allocator>)
(C++11)
rend returns a reverse iterator to the end
crend (public member function of std::vector<T,Allocator>)
(C++11)

Capacity¶

empty checks whether the container is empty
(public member function of std::vector<T,Allocator>)
size returns the number of elements
(public member function of std::vector<T,Allocator>)
max_size returns the maximum possible number of elements
(public member function of std::vector<T,Allocator>)
reserve reserves storage
(public member function of std::vector<T,Allocator>)
returns the number of elements that can be held in currently allocated
capacity storage
(public member function of std::vector<T,Allocator>)

Modifiers¶

clear clears the contents
(public member function of std::vector<T,Allocator>)
insert inserts elements
(public member function of std::vector<T,Allocator>)
emplace constructs element in-place
(C++11) (public member function of std::vector<T,Allocator>)
erase erases elements
(public member function of std::vector<T,Allocator>)
push_back adds an element to the end
(public member function of std::vector<T,Allocator>)
emplace_back constructs an element in-place at the end
(C++11) (public member function of std::vector<T,Allocator>)
pop_back removes the last element
(public member function of std::vector<T,Allocator>)
resize changes the number of elements stored
(public member function of std::vector<T,Allocator>)
swap swaps the contents
(public member function of std::vector<T,Allocator>)

vector<bool> specific modifiers¶

flip flips all the bits
(public member function)
swap swaps two std::vector<bool>::references
[static] (public static member function)

Non-member functions¶

operator==
operator!=
operator<
operator<=
operator>
operator>= lexicographically compares the values in the vector
operator<=> (function template)
(removed in C++20)
(removed in C++20)
(removed in C++20)
(removed in C++20)
(removed in C++20)
(C++20)
std::swap(std::vector) specializes the std::swap algorithm
(function template)
erase(std::vector) Erases all elements satisfying specific criteria
erase_if(std::vector) (function template)
(C++20)

Helper classes¶

std::hash<std::vector<bool>> hash support for std::vector<bool>
(C++11) (class template specialization)

Deduction guides (C++17)

Notes¶

If the size of the bitset is known at compile time, std::bitset may be used, which
offers a richer set of member functions. In addition, boost::dynamic_bitset exists
as an alternative to std::vector<bool>.

Since its representation may be optimized, std::vector<bool> does not necessarily
meet all Container or SequenceContainer requirements. For example, because
std::vector<bool>::iterator is implementation-defined, it may not satisfy the
LegacyForwardIterator requirement. Use of algorithms such as std::search that
require LegacyForwardIterators may result in either compile-time or run-time errors.

The Boost.Container version of vector does not specialize for bool.

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2187 C++11 specializations for bool lacked emplace and added
emplace_back member functions