public member function
<deque>
std::deque::push_front
void push_front (const value_type& val);
void push_front (const value_type& val);
void push_front (value_type&& val);
Insert element at beginning
Inserts a new element at the beginning of the deque container, right before its current first element. The content of val is copied (or moved) to the inserted element.
This effectively increases the container size by one.
Parameters
- val
- Value to be copied (or moved) to the inserted element.
Member type value_type is the type of the elements in the container, defined in deque as an alias of its first template parameter (T).
Return value
none
The storage for the new elements is allocated using the container's allocator, 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::push_front
#include <iostream>
#include <deque>
int main ()
{
std::deque<int> mydeque (2,100); // two ints with a value of 100
mydeque.push_front (200);
mydeque.push_front (300);
std::cout << "mydeque contains:";
for (std::deque<int>::iterator it = mydeque.begin(); it != mydeque.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
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Output:
Iterator validity
All iterators related to this container are invalidated. Pointers and references to elements in the container remain valid, referring to the same elements they were referring to before the call.
Data races
The container is modified.
No existing elements are accessed (although see iterator validity above).
Exception safety
Strong guarantee: if an exception is thrown, there are no changes in the container.
If allocator_traits::construct is not supported with val as argument, it causes undefined behavior.