std::deque<T,Allocator>::emplace_back (3) - Linux Manuals
std::deque<T,Allocator>::emplace_back: std::deque<T,Allocator>::emplace_back
Command to display std::deque<T,Allocator>::emplace_back
manual in Linux: $ man 3 std::deque<T,Allocator>::emplace_back
NAME
std::deque<T,Allocator>::emplace_back - std::deque<T,Allocator>::emplace_back
Synopsis
template< class... Args > (since C++11)
void emplace_back( Args&&... args ); (until C++17)
template< class... Args > (since C++17)
reference emplace_back( Args&&... args );
Appends a new element to the end of the container. The element is constructed through std::allocator_traits::construct, which typically uses placement-new to construct the element in-place at the location provided by the container. The arguments args... are forwarded to the constructor as std::forward<Args>(args)....
All iterators, including the past-the-end iterator, are invalidated. No references are invalidated.
Parameters
args - arguments to forward to the constructor of the element
Type requirements
-
T (the container's element type) must meet the requirements of EmplaceConstructible.
Return value
(none) (until C++17)
A reference to the inserted element. (since C++17)
Complexity
Constant.
Exceptions
If an exception is thrown, this function has no effect (strong exception guarantee).
Example
The following code uses emplace_back to append an object of type President to a std::deque. It demonstrates how emplace_back forwards parameters to the President constructor and shows how using emplace_back avoids the extra copy or move operation required when using push_back.
// Run this code
#include <deque>
#include <string>
#include <iostream>
struct President
{
std::string name;
std::string country;
int year;
President(std::string p_name, std::string p_country, int p_year)
: name(std::move(p_name)), country(std::move(p_country)), year(p_year)
{
std::cout << "I am being constructed.\n";
}
President(President&& other)
: name(std::move(other.name)), country(std::move(other.country)), year(other.year)
{
std::cout << "I am being moved.\n";
}
President& operator=(const President& other) = default;
};
int main()
{
std::deque<President> elections;
std::cout << "emplace_back:\n";
elections.emplace_back("Nelson Mandela", "South Africa", 1994);
std::deque<President> reElections;
std::cout << "\npush_back:\n";
reElections.push_back(President("Franklin Delano Roosevelt", "the USA", 1936));
std::cout << "\nContents:\n";
for (President const& president: elections) {
std::cout << president.name << " was elected president of "
<< president.country << " in " << president.year << ".\n";
}
for (President const& president: reElections) {
std::cout << president.name << " was re-elected president of "
<< president.country << " in " << president.year << ".\n";
}
}
Output:
emplace_back:
I am being constructed.
push_back:
I am being constructed.
I am being moved.
See also
adds an element to the end
push_back (public member function)
Pages related to std::deque<T,Allocator>::emplace_back
- std::deque<T,Allocator>::emplace_front (3) - std::deque<T,Allocator>::emplace_front
- std::deque<T,Allocator>::emplace (3) - std::deque<T,Allocator>::emplace
- std::deque<T,Allocator>::empty (3) - std::deque<T,Allocator>::empty
- std::deque<T,Allocator>::end,std::deque<T,Allocator>::cend (3) - std::deque<T,Allocator>::end,std::deque<T,Allocator>::cend
- std::deque<T,Allocator>::erase (3) - std::deque<T,Allocator>::erase
- std::deque<T,Allocator>::assign (3) - std::deque<T,Allocator>::assign
- std::deque<T,Allocator>::at (3) - std::deque<T,Allocator>::at
- std::deque<T,Allocator>::back (3) - std::deque<T,Allocator>::back
- std::deque<T,Allocator>::begin,std::deque<T,Allocator>::cbegin (3) - std::deque<T,Allocator>::begin,std::deque<T,Allocator>::cbegin
- std::deque<T,Allocator>::clear (3) - std::deque<T,Allocator>::clear
- std::deque<T,Allocator>::deque (3) - std::deque<T,Allocator>::deque
- std::deque<T,Allocator>::front (3) - std::deque<T,Allocator>::front
- std::deque<T,Allocator>::get_allocator (3) - std::deque<T,Allocator>::get_allocator
- std::deque<T,Allocator>::insert (3) - std::deque<T,Allocator>::insert
- std::deque<T,Allocator>::max_size (3) - std::deque<T,Allocator>::max_size
- std::deque<T,Allocator>::operator= (3) - std::deque<T,Allocator>::operator=
- std::deque<T,Allocator>::operator[] (3) - std::deque<T,Allocator>::operator[]
- std::deque<T,Allocator>::pop_back (3) - std::deque<T,Allocator>::pop_back
- std::deque<T,Allocator>::pop_front (3) - std::deque<T,Allocator>::pop_front
- std::deque<T,Allocator>::push_back (3) - std::deque<T,Allocator>::push_back
- std::deque<T,Allocator>::push_front (3) - std::deque<T,Allocator>::push_front
- std::deque<T,Allocator>::rbegin,std::deque<T,Allocator>::crbegin (3) - std::deque<T,Allocator>::rbegin,std::deque<T,Allocator>::crbegin
- std::deque<T,Allocator>::rend,std::deque<T,Allocator>::crend (3) - std::deque<T,Allocator>::rend,std::deque<T,Allocator>::crend
- std::deque<T,Allocator>::resize (3) - std::deque<T,Allocator>::resize
- std::deque<T,Allocator>::shrink_to_fit (3) - std::deque<T,Allocator>::shrink_to_fit
- std::deque<T,Allocator>::size (3) - std::deque<T,Allocator>::size
- std::deque<T,Allocator>::swap (3) - std::deque<T,Allocator>::swap
- std::deque<T,Allocator>::~deque (3) - std::deque<T,Allocator>::~deque
- std::deque (3) - std::deque