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Difference between revisions of "cpp/container/vector bool"

From cppreference.com
< cpp‎ | container
(LWG 2187, treated ad DR by libc++/libstdc++)
m (→‎Notes: +FTM)
 
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{{cpp/title|vector<bool>}}
 
{{cpp/title|vector<bool>}}
 
{{cpp/container/vector_bool/navbar}}
 
{{cpp/container/vector_bool/navbar}}
−
{{ddcl | header=vector |
+
{{ddcl|header=vector|
−
template<class Allocator>
+
template<
−
class vector<bool, Allocator>;
+
    class Allocator
−
}}  
+
> class vector<bool, Allocator>;
 +
}}
  
−
{{c|std::vector<bool>}} is a possibly space-efficient specialization of {{lc|std::vector}} for the type {{c|bool}}.  
+
{{c|std::vector<bool>}} is a possibly space-efficient specialization of {{lc|std::vector}} for the type {{c|bool}}.
  
 
The manner in which {{c|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 {{c|sizeof(bool)}} bytes.
 
The manner in which {{c|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 {{c|sizeof(bool)}} bytes.
Line 19: Line 20:
 
===Member types===
 
===Member types===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc hitem | Member type | Definition}}
+
{{dsc hitem|Member type|Definition}}
−
{{dsc inc | cpp/container/dsc value_type | vector_bool}}
+
{{dsc inc|cpp/container/dsc value_type|vector_bool}}
−
{{dsc inc | cpp/container/dsc allocator_type | vector_bool}}
+
{{dsc inc|cpp/container/dsc allocator_type|vector_bool}}
−
{{dsc inc | cpp/container/dsc size_type | vector_bool}}
+
{{dsc inc|cpp/container/dsc size_type|vector_bool}}
−
{{dsc inc | cpp/container/dsc difference_type | vector_bool}}
+
{{dsc inc|cpp/container/dsc difference_type|vector_bool}}
−
{{dsc class | cpp/container/vector_bool/reference | proxy class representing a reference to a single bool}}
+
{{dsc class|cpp/container/vector_bool/reference|proxy class representing a reference to a single bool}}
−
{{dsc inc | cpp/container/dsc const_reference | vector_bool}}
+
{{dsc inc|cpp/container/dsc const_reference|vector_bool}}
−
{{dsc inc | cpp/container/dsc pointer | vector_bool}}
+
{{dsc inc|cpp/container/dsc pointer|vector_bool}}
−
{{dsc inc | cpp/container/dsc const_pointer | vector_bool}}
+
{{dsc inc|cpp/container/dsc const_pointer|vector_bool}}
−
{{dsc inc | cpp/container/dsc iterator | vector_bool}}
+
{{dsc inc|cpp/container/dsc iterator|vector_bool}}
−
{{dsc inc | cpp/container/dsc const_iterator | vector_bool}}
+
{{dsc inc|cpp/container/dsc const_iterator|vector_bool}}
−
{{dsc inc | cpp/container/dsc reverse_iterator | vector_bool}}
+
{{dsc inc|cpp/container/dsc reverse_iterator|vector_bool}}
−
{{dsc inc | cpp/container/dsc const_reverse_iterator | vector_bool}}
+
{{dsc inc|cpp/container/dsc const_reverse_iterator|vector_bool}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Member functions===
 
===Member functions===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/container/dsc constructor | vector}}
+
{{dsc inc|cpp/container/dsc constructor|vector}}
−
{{dsc inc | cpp/container/dsc destructor | vector}}
+
{{dsc inc|cpp/container/dsc destructor|vector}}
−
{{dsc inc | cpp/container/dsc operator{{=}} | vector}}
+
{{dsc inc|cpp/container/dsc operator{{=}}|vector}}
−
{{dsc inc | cpp/container/dsc assign | vector}}
+
{{dsc inc|cpp/container/dsc assign|vector}}
−
{{dsc inc | cpp/container/dsc get_allocator | vector}}
+
{{dsc inc|cpp/container/dsc get_allocator|vector}}
  
−
{{dsc h2 | Element access}}
+
{{dsc h2|Element access}}
−
{{dsc inc | cpp/container/dsc at | vector}}
+
{{dsc inc|cpp/container/dsc at|vector}}
−
{{dsc inc | cpp/container/dsc operator_at | vector}}
+
{{dsc inc|cpp/container/dsc operator_at|vector}}
−
{{dsc inc | cpp/container/dsc front | vector}}
+
{{dsc inc|cpp/container/dsc front|vector}}
−
{{dsc inc | cpp/container/dsc back | vector}}
+
{{dsc inc|cpp/container/dsc back|vector}}
  
−
{{dsc h2 | Iterators}}
+
{{dsc h2|Iterators}}
−
{{dsc inc | cpp/container/dsc begin | vector}}
+
{{dsc inc|cpp/container/dsc begin|vector}}
−
{{dsc inc | cpp/container/dsc end | vector}}
+
{{dsc inc|cpp/container/dsc end|vector}}
−
{{dsc inc | cpp/container/dsc rbegin | vector}}
+
{{dsc inc|cpp/container/dsc rbegin|vector}}
−
{{dsc inc | cpp/container/dsc rend | vector}}
+
{{dsc inc|cpp/container/dsc rend|vector}}
  
−
{{dsc h2 | Capacity}}
+
{{dsc h2|Capacity}}
−
{{dsc inc | cpp/container/dsc empty | vector}}
+
{{dsc inc|cpp/container/dsc empty|vector}}
−
{{dsc inc | cpp/container/dsc size | vector}}
+
{{dsc inc|cpp/container/dsc size|vector}}
−
{{dsc inc | cpp/container/dsc max_size | vector}}
+
{{dsc inc|cpp/container/dsc max_size|vector}}
−
{{dsc inc | cpp/container/dsc reserve | vector}}
+
{{dsc inc|cpp/container/dsc reserve|vector}}
−
{{dsc inc | cpp/container/dsc capacity | vector}}
+
{{dsc inc|cpp/container/dsc capacity|vector}}
  
−
{{dsc h2 | Modifiers}}
+
{{dsc h2|Modifiers}}
−
{{dsc inc | cpp/container/dsc clear | vector}}
+
{{dsc inc|cpp/container/dsc clear|vector}}
−
{{dsc inc | cpp/container/dsc insert | vector}}
+
{{dsc inc|cpp/container/dsc insert|vector}}
−
{{dsc inc | cpp/container/dsc emplace | vector}}
+
{{dsc inc|cpp/container/dsc emplace|vector}}
−
{{dsc inc | cpp/container/dsc erase | vector}}
+
{{dsc inc|cpp/container/dsc erase|vector}}
−
{{dsc inc | cpp/container/dsc push_back | vector}}
+
{{dsc inc|cpp/container/dsc push_back|vector}}
−
{{dsc inc | cpp/container/dsc emplace_back | vector}}
+
{{dsc inc|cpp/container/dsc emplace_back|vector}}
−
{{dsc inc | cpp/container/dsc pop_back | vector}}
+
{{dsc inc|cpp/container/dsc pop_back|vector}}
−
{{dsc inc | cpp/container/dsc resize | vector}}
+
{{dsc inc|cpp/container/dsc resize|vector}}
−
{{dsc inc | cpp/container/dsc swap | vector}}
+
{{dsc inc|cpp/container/dsc swap|vector}}
  
−
{{dsc h2 | {{tt|vector<bool>}} specific modifiers}}
+
{{dsc h2|{{tt|vector<bool>}} specific modifiers}}
−
{{dsc inc | cpp/container/vector_bool/dsc flip}}
+
{{dsc inc|cpp/container/vector_bool/dsc flip}}
−
{{dsc inc | cpp/container/vector_bool/dsc swap}}
+
{{dsc inc|cpp/container/vector_bool/dsc swap}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Non-member functions===
 
===Non-member functions===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/container/dsc operator_cmp | vector}}
+
{{dsc inc|cpp/container/dsc operator_cmp|vector}}
−
{{dsc inc | cpp/container/dsc swap2 | vector}}
+
{{dsc inc|cpp/container/dsc swap2|vector}}
−
{{dsc inc | cpp/container/dsc erase seq | vector}}
+
{{dsc inc|cpp/container/dsc erase seq|vector}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Helper classes===
 
===Helper classes===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/container/vector_bool/dsc hash}}
+
{{dsc inc|cpp/container/vector_bool/dsc hash}}
 
{{dsc end}}
 
{{dsc end}}
  
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===Notes===
 
===Notes===
−
If the size of the bitset is known at compile time, {{lc|std::bitset}} may be used, which offers a richer set of member functions. In addition, [http://www.boost.org/doc/libs/release/libs/dynamic_bitset/dynamic_bitset.html boost::dynamic_bitset] exists as an alternative to {{tt|std::vector<bool>}}.
+
If the size of the bitset is known at compile time, {{lc|std::bitset}} may be used, which offers a richer set of member functions. In addition, [https://www.boost.org/doc/libs/release/libs/dynamic_bitset/dynamic_bitset.html {{tt|boost::dynamic_bitset}}] exists as an alternative to {{tt|std::vector<bool>}}.
  
−
Since its representation may be optimized, {{c|std::vector<bool>}} does not necessarily meet all {{named req|Container}} or {{named req|SequenceContainer}} requirements. For example, because {{c|std::vector<bool>::iterator}} is implementation-defined, it may not satisfy the {{named req|ForwardIterator}} requirement.  Use of algorithms such as {{lc|std::search}} that require {{named req|ForwardIterator}}s may result in [http://www.boost.org/doc/libs/1_75_0/libs/dynamic_bitset/dynamic_bitset.html#rationale either compile-time or run-time errors].
+
Since its representation may be optimized, {{c|std::vector<bool>}} does not necessarily meet all {{named req|Container}} or {{named req|SequenceContainer}} requirements. For example, because {{c|std::vector<bool>::iterator}} is implementation-defined, it may not satisfy the {{named req|ForwardIterator}} requirement.  Use of algorithms such as {{lc|std::search}} that require {{named req|ForwardIterator}}s may result in [https://www.boost.org/doc/libs/release/libs/dynamic_bitset/dynamic_bitset.html#rationale either compile-time or run-time errors].
  
−
The [https://www.boost.org/doc/libs/release/doc/html/boost/container/vector.html Boost.Container version of {{tt|vector}}] does not specialize for {{tt|bool}}.
+
The [https://www.boost.org/doc/libs/release/doc/html/boost/container/vector.html Boost.Container version of {{tt|vector}}] does not specialize for {{c|bool}}.
 +
 
 +
===Notes===
 +
{{ftm begin|std=1|comment=1}}
 +
{{ftm|__cpp_lib_containers_ranges|value=202202L|std=C++23|Ranges construction and insertion for containers}}
 +
{{ftm end}}
  
 
===Defect reports===
 
===Defect reports===

Latest revision as of 10:50, 29 April 2023

 
C++
 
Containers library
 
std::vector<bool>
Member functions
Element access
Iterators
Capacity
Modifiers
std::vector<bool> specific
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Helper classes
(C++11)
Deduction guides(C++17)
 
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.

Contents

[edit] Member types

Member type Definition
value_type bool[edit]
allocator_type Allocator[edit]
size_type implementation-defined[edit]
difference_type implementation-defined[edit]
proxy class representing a reference to a single bool
(class)
const_reference bool[edit]
pointer implementation-defined[edit]
const_pointer implementation-defined[edit]
iterator

implementation-defined

(until C++20)

implementation-defined ConstexprIterator

(since C++20)
[edit]
const_iterator

implementation-defined

(until C++20)

implementation-defined ConstexprIterator

(since C++20)
[edit]
reverse_iterator std::reverse_iterator<iterator>[edit]
const_reverse_iterator std::reverse_iterator<const_iterator>[edit]

[edit] Member functions

 constructs the vector
(public member function of std::vector<T,Allocator>) [edit]
destructs the vector
(public member function of std::vector<T,Allocator>) [edit]
assigns values to the container
(public member function of std::vector<T,Allocator>) [edit]
assigns values to the container
(public member function of std::vector<T,Allocator>) [edit]
returns the associated allocator
(public member function of std::vector<T,Allocator>) [edit]
Element access
access specified element with bounds checking
(public member function of std::vector<T,Allocator>) [edit]
access specified element
(public member function of std::vector<T,Allocator>) [edit]
access the first element
(public member function of std::vector<T,Allocator>) [edit]
access the last element
(public member function of std::vector<T,Allocator>) [edit]
Iterators
(C++11)
 returns an iterator to the beginning
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 returns an iterator to the end
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 returns a reverse iterator to the beginning
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 returns a reverse iterator to the end
(public member function of std::vector<T,Allocator>) [edit]
Capacity
checks whether the container is empty
(public member function of std::vector<T,Allocator>) [edit]
returns the number of elements
(public member function of std::vector<T,Allocator>) [edit]
returns the maximum possible number of elements
(public member function of std::vector<T,Allocator>) [edit]
reserves storage
(public member function of std::vector<T,Allocator>) [edit]
returns the number of elements that can be held in currently allocated storage
(public member function of std::vector<T,Allocator>) [edit]
Modifiers
clears the contents
(public member function of std::vector<T,Allocator>) [edit]
inserts elements
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 constructs element in-place
(public member function of std::vector<T,Allocator>) [edit]
erases elements
(public member function of std::vector<T,Allocator>) [edit]
adds an element to the end
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 constructs an element in-place at the end
(public member function of std::vector<T,Allocator>) [edit]
removes the last element
(public member function of std::vector<T,Allocator>) [edit]
changes the number of elements stored
(public member function of std::vector<T,Allocator>) [edit]
swaps the contents
(public member function of std::vector<T,Allocator>) [edit]
vector<bool> specific modifiers
flips all the bits
(public member function) [edit]
[static]
 swaps two std::vector<bool>::references
(public static member function) [edit]

[edit] Non-member functions

(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)
 lexicographically compares the values of two vectors
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++20)
 erases all elements satisfying specific criteria
(function template) [edit]

[edit] Helper classes

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

[edit] Deduction guides (C++17)

[edit] 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.

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges construction and insertion for containers

[edit] 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 emplace_back member functions added
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