Difference between revisions of "Template:cpp/container/push back"
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If {{tt|T}}'s move constructor is not {{c|noexcept}} and T is not {{named req|CopyInsertable}} into {{tt|*this}}, vector will use the throwing move constructor. If it throws, the guarantee is waived and the effects are unspecified. | If {{tt|T}}'s move constructor is not {{c|noexcept}} and T is not {{named req|CopyInsertable}} into {{tt|*this}}, vector will use the throwing move constructor. If it throws, the guarantee is waived and the effects are unspecified. | ||
}} | }} | ||
| − | }} | + | }}{{#ifeq: {{{1|vector}}} | vector | |
| − | {{#ifeq: {{{1|}}} | vector | | + | |
===Notes=== | ===Notes=== | ||
| − | Calling {{tt|push_back}} will cause reallocation (when {{ | + | Calling {{tt|push_back}} will cause reallocation (when {{lc|size}}{{tt|()+1 > <!-- -->}}{{lc|capacity}}{{tt|()}}), so some implementations also throw {{lc|std::length_error}} when {{tt|push_back}} causes a reallocation that would exceed {{lc|max_size}} (due to implicitly calling an equivalent of {{lc|reserve}}{{tt|(}}{{lc|size}}{{tt|()+1))}}. |
}} | }} | ||
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===Example=== | ===Example=== | ||
{{example | {{example | ||
Revision as of 13:53, 17 July 2022
| void push_back( const T& value ); |
(1) | (since {std}) |
| void push_back( T&& value ); |
(2) | (since C++11) |
Appends the given element value to the end of the container.
1) The new element is initialized as a copy of
value.2)
value is moved into the new element.| Information on iterator invalidation is copied from here |
Contents |
Parameters
| value | - | the value of the element to append |
| Type requirements | ||
-T must meet the requirements of CopyInsertable in order to use overload (1).
| ||
-T must meet the requirements of MoveInsertable in order to use overload (2).
| ||
Return value
(none)
Complexity
| Templated information. See page source. |
Exceptions
If an exception is thrown (which can be due to Allocator::allocate() or element copy/move constructor/assignment), this function has no effect (strong exception guarantee).
Notes
Calling push_back will cause reallocation (when size()+1 > capacity()), so some implementations also throw std::length_error when push_back causes a reallocation that would exceed max_size (due to implicitly calling an equivalent of reserve(size()+1)).
Example
Run this code
#include <list> #include <iostream> #include <iomanip> #include <string> int main() { std::list<std::string> letters; letters.push_back("abc"); std::string s{"def"}; letters.push_back(std::move(s)); std::cout << "std::list `letters` holds: "; for (auto&& e : letters) std::cout << std::quoted(e) << ' '; std::cout << "\nMoved-from string `s` holds: " << std::quoted(s) << '\n'; }
Possible output:
std::list `letters` holds: "abc" "def" Moved-from string `s` holds: ""
See also
| (C++11) |
constructs an element in-place at the end (public member function of std::{{{1}}})
|
| inserts an element to the beginning (public member function of std::{{{1}}})
| |
| removes the last element (public member function of std::{{{1}}})
| |
| creates a std::back_insert_iterator of type inferred from the argument (function template) |
