RetroSearch Browse

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://en.cppreference.com/w/cpp/language/../container/deque/resize.html below:

std::deque<T,Allocator>::resize - cppreference.com

void resize( size_type count );

(1) (constexpr since C++26)

void resize( size_type count, const value_type& value );

(2) (constexpr since C++26)

Resizes the container to contain count elements:

If count is equal to the current size, does nothing.
If the current size is greater than count, the container is reduced to its first count elements.
If the current size is less than count, then:

1)

Additional

copies of T()(until C++11)default-inserted elements(since C++11)

are appended.

2) Additional copies of value are appended.

[edit] Parameters count - new size of the container value - the value to initialize the new elements with Type requirements - [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);
}

Output:

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.

DR Applied to Behavior as published Correct behavior LWG 679 C++98 resize() passed value by value passes by const reference LWG 1418 C++98 the behavior of resize(size()) was not specified specified LWG 2033 C++11 1. elements were removed by using erase()^[1]
2. T was not required to be MoveInsertable 1. uses pop_back()
2. required LWG 2066 C++11 overload (1) did not have the exception
safety guarantee of overload (2) added LWG 2160 C++11 elements were removed by using pop_back()^[2]
due to the resolution of LWG 2033 does not specify the method
of removing elements

â 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.
â Removing elements by using pop_back() implies that the elements are required to be removed from back to front.

[edit] See also returns the maximum possible number of elements
(public member function) [edit] returns the number of elements
(public member function) [edit] checks whether the container is empty
(public member function) [edit]

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4