std::deque<T,Allocator>::resize

• 1 Parameters
• 2 Complexity
• 3 Notes
• 4 Example
• 5 Defect reports
• 6 See also

[edit] Complexity

Linear in the difference between the current size and count.

Notes

If value-initialization in overload (1) is undesirable, for example, if the elements are of non-class type and zeroing out is not needed, it can be avoided by providing a custom Allocator::construct.

[edit] Example

#include <deque>
#include <iostream>
 
void print(auto rem, const std::deque <int>& c)
{
 for (std::cout << rem; const int el : c)
 std::cout << el << ' ';
 std::cout << '\n';
}
 
int main()
{
 std::deque <int> c = {1, 2, 3};
 print("The deque holds: ", c);
 
 c.resize(5);
 print("After resize up to 5: ", c);
 
 c.resize(2);
 print("After resize down to 2: ", c);
 
 c.resize(6, 4);
 print("After resize up to 6 (initializer = 4): ", c);
}

The deque holds: 1 2 3
After resize up to 5: 1 2 3 0 0
After resize down to 2: 1 2
After resize up to 6 (initializer = 4): 1 2 4 4 4 4

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

1. ↑ erase() can remove elements in the middle of a deque, so the value type is required to be MoveAssignable so that the elements following the removed section can be moved forward to fill the gap. However, resize() can only remove elements at the end of the deque, making the MoveAssignable unnecessary.
2. ↑ Removing elements by using pop_back() implies that the elements are required to be removed from back to front.

[edit] See also