std::inplace_vector<T,N>::emplace

template< class... Args >
constexpr iterator emplace( const_iterator position, Args&&... args );

(since C++26)

Inserts a new element into the container directly before pos. Typically, the element is constructed in-place using placement new at the location provided by the container. The arguments args... are forwarded to the constructor with std::forward<Args>(args)....

Parameters

pos	-	iterator before which the new element will be constructed
args	-	arguments to forward to the constructor of the element
Type requirements
-`T` must meet the requirements of MoveAssignable, MoveInsertable and EmplaceConstructible.

Return value

An iterator to the inserted element.

Complexity

Linear in the distance between pos and end().

Exceptions

Throws std::bad_alloc if before the invocation size() == capacity(). The function has no effects (strong exception safety guarantee).

Any exception thrown by initialization of inserted element or by any LegacyInputIterator operation. Elements in [0, pos) are not modified.

Example

#include <cassert>
#include <inplace_vector>
#include <iostream>
#include <new>
#include <utility>

int main()
{
    using P = std::pair<int, int>;
    using I = std::inplace_vector<P, 3>;
    auto nums = I{{0, 1}, {2, 3}};
    
    auto it = nums.emplace(nums.begin() + 1, -1, -2);
    assert((*it == P{-1, -2}));
    assert((nums == I{P{0, 1}, {-1, -2}, {2, 3}}));
    
    try
    {
        nums.emplace(nums.begin(), 1, 3); // throws: no space
    }
    catch(const std::bad_alloc& ex)
    {
        std::cout << ex.what() << '\n';
    }
}

Possible output:

std::bad_alloc