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
,
value
are appended.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). |
(none).
Linear in the difference between the current size and count
.
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
.
#include <iostream> #include <list> int main() { std::list<int> c = {1, 2, 3}; std::cout << "The list holds: "; for (const auto& el: c) std::cout << el << ' '; std::cout << '\n'; c.resize(5); std::cout << "After resize up to 5: "; for (const auto& el: c) std::cout << el << ' '; std::cout << '\n'; c.resize(2); std::cout << "After resize down to 2: "; for (const auto& el: c) std::cout << el << ' '; std::cout << '\n'; c.resize(6, 4); std::cout << "After resize up to 6 (initializer = 4): "; for (const auto& el: c) std::cout << el << ' '; std::cout << '\n'; }
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
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 |
returns the number of elements (public member function) |
|
inserts elements (public member function) |
|
erases elements (public member function) |
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