std::list<T,Allocator>::resize
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list::resize
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
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:
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
-
If the following condition is satisfied, the behavior is undefined:
(since C++11)[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
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 |