std::forward_list swap() method
- since C++17
- since C++11
// Non const version only
void swap( forward_list& other ) noexcept(/* see below */);
// Non const version only
void swap( forward_list& other );
Exchanges the contents of the container with those of other
.
Does not invoke any move, copy, or swap operations on individual elements.
All iterators and references remain valid. It is unspecified whether an iterator holding the past-the-end value in this container will refer to this or the other container after the operation.
- since C++11
If std::allocator_traits<allocator_type>::propagate_on_container_swap::value
is true
.
then the allocators are exchanged using an unqualified call to non-member swap.
Otherwise, they are not swapped.
If get_allocator() != other.get_allocator()
, the behavior is undefined
Parameters
other
- the container to exchange the contents with
Return value
(none)
Complexity
Constant - O(1).
Exceptions
- since C++17
- until C++17
noexcept(std::allocator_traits<Allocator>::is_always_equal::value)
Example
#include <iostream>
#include <forward_list>
template<class Os, class Co> Os& operator<<(Os& os, const Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}
int main()
{
std::forward_list<int> a1{1, 2, 3}, a2{4, 5};
auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());
int& ref1 = a1.front();
int& ref2 = a2.front();
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
a1.swap(a2);
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
// Note that after swap the iterators and references stay associated with their
// original elements, e.g. it1 that pointed to an element in 'a1' with value 2
// still points to the same element, though this element was moved into 'a2'.
}
{ 1 2 3 } { 4 5 } 2 5 1 4
{ 4 5 } { 1 2 3 } 2 5 1 4
Hover to see the original license.