std::list<T,Allocator>::resize
From cppreference.com
void resize( size_type count ); |
(1) | |
void resize( size_type count, const value_type& value ); |
(2) | |
Resizes the container to contain count elements, does nothing if count == size().
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 default-inserted elements are appended.
2) Additional copies of
value are appended.Parameters
| count | - | new size of the container |
| value | - | the value to initialize the new elements with |
| Type requirements | ||
-T must meet the requirements of DefaultInsertable in order to use overload (1).
| ||
-T must meet the requirements of CopyInsertable in order to use overload (2).
| ||
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.
Example
Run this code
#include <list>
#include <iostream>
void print(auto rem, const std::list<int>& c)
{
for (std::cout << rem; const int el : c)
std::cout << el << ' ';
std::cout << '\n';
}
int main()
{
std::list<int> c = {1, 2, 3};
print("The list 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 list 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 132 | C++98 | random-access iterators were used to determine the erase range | use bidirectional iterators |
| LWG 679 | C++98 | resize() passed value by value
|
passes by const reference |
| LWG 1420 | C++98 | the behavior of resize(size()) was not specified
|
specified |
See also
| returns the maximum possible number of elements (public member function) | |
| returns the number of elements (public member function) | |
| checks whether the container is empty (public member function) |