public member function

std::deque::emplace_front

<deque>
template <class... Args>
void emplace_front (Args&&... args);
Construct and insert element at beginning
Inserts a new element at the beginning of the deque, right before its current first element. This new element is constructed in place using args as the arguments for its constructor.

This effectively increases the container size by one.

A similar member function exists, push_front, which either copies or moves an existing object into the container.

Parameters

args
Arguments passed to the constructor of the new element.

Return value

none.

The storage for the new element is allocated using allocator_traits<allocator_type>::construct(), which may throw exceptions on failure (for the default allocator, bad_alloc is thrown if the allocation request does not succeed).

Example

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// deque::emplace_from
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque = {10,20,30};

  mydeque.emplace_front (111);
  mydeque.emplace_front (222);

  std::cout << "mydeque contains:";
  for (auto& x: mydeque)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

Output:
mydeque contains: 222 111 10 20 30

Complexity

Constant.

Iterator validity

All iterators related to this container are invalidated, but pointers and references remain valid, referring to the same elements they were referring to before the call.

See also

deque::insert_front