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std::inplace_vector<T,N>::resize - cppreference.com

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constexpr void resize( size_type count );

 (1) (since C++26)

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

 (2) (since C++26)

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:

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.

Exceptions

1,2) Throws std::bad_alloc if count > N.

If an exception is thrown for any reason, these functions have no effect (strong exception safety guarantee).

Example

#include <inplace_vector>
#include <print>

int main()
{
    std::inplace_vector<int, 6> v(6, 9);
    std::println("Initially, v = {}", v);

    v.resize(2);
    std::println("After resize(2), v = {}", v);

    v.resize(4);
    std::println("After resize(4), v = {}", v);

    v.resize(6, -1);
    std::println("After resize(6, -1), v = {}", v);

    try
    {
        std::print("Trying resize(13): ");
        v.resize(13); // throws, because count > N; v is left unchanged
    }
    catch(const std::bad_alloc& ex)
    {
        std::println("ex.what(): {}", ex.what());
    }
    std::println("After exception, v = {}", v);
}

Possible output: 

Initially, v = [9, 9, 9, 9, 9, 9]
After resize(2), v = [9, 9]
After resize(4), v = [9, 9, 0, 0]
After resize(6, -1), v = [9, 9, 0, 0, -1, -1]
Trying resize(13): ex.what(): std::bad_alloc
After exception, v = [9, 9, 0, 0, -1, -1]

See also

returns the maximum possible number of elements
(public static member function) [edit]
returns the number of elements
(public member function) [edit]
returns the number of elements that can be held in currently allocated storage
(public static member function) [edit]
checks whether the container is empty
(public member function) [edit]