std::inplace_vector<T,N>:: inplace_vector

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C++
Containers library
std::inplace_vector
Member types
Member functions
Non-member functions
constexpr inplace_vector ( ) noexcept ;
(1) (since C++26)
constexpr explicit inplace_vector ( size_type count ) ;
(2) (since C++26)
constexpr inplace_vector ( size_type count, const T & value ) ;
(3) (since C++26)
template < class InputIt >
constexpr inplace_vector ( InputIt first, InputIt last ) ;
(4) (since C++26)
template < /*container-compatible-range*/ < T > R >
constexpr inplace_vector ( std:: from_range_t , R && rg ) ;
(5) (since C++26)
constexpr inplace_vector ( const inplace_vector & other ) ;
(6) (since C++26)
constexpr inplace_vector ( inplace_vector && other )
noexcept ( N == 0 || std:: is_nothrow_move_constructible_v < T > ) ;
(7) (since C++26)
constexpr inplace_vector ( std:: initializer_list < T > init ) ;
(8) (since C++26)

Constructs a new inplace_vector from a variety of data sources.

1) Constructs an empty inplace_vector whose data ( ) == nullptr and size ( ) == 0 .
2) Constructs an inplace_vector with count default-inserted elements.
3) Constructs an inplace_vector with count copies of elements with value value .
4) Constructs an inplace_vector with the contents of the range [ first , last ) .
5) Constructs an inplace_vector with the contents of the range rg .
For the definition of /*container-compatible-range*/ , see ranges::to .
6) A copy constructor . Constructs an inplace_vector with the copy of the contents of other .
The constructor is a trivial copy constructor if N > 0 and std:: is_trivially_copy_constructible_v < T > are both true .
7) A move constructor . Constructs an inplace_vector with the contents of other using move semantics.
The constructor is a trivial move constructor if N > 0 and std:: is_trivially_move_constructible_v < T > are both true .
8) Constructs an inplace_vector with the contents of the initializer list init .

Parameters

count - the size of the container
value - the value to initialize elements of the container with
first, last - the range [ first , last ) to copy the elements from
rg - the range of values to initialize elements of the container with
other - another inplace_vector to be used as source to initialize the elements of the container with
init - initializer list to initialize the elements of the container with
Type requirements
-
T must meet the requirements of DefaultInsertable in order to use overloads (2,3).

Complexity

1) Constant.
2,3) Linear in count .
4) Linear in std:: distance ( first, last ) .
5) Linear in std :: ranges:: distance ( rg ) .
6,7) Linear in size of other .
8) Linear in size of init .

Exceptions

2,3) Throws std::bad_alloc if count > N .
5) Throws std::bad_alloc if std :: ranges:: size ( rg ) > N .
8) Throws std::bad_alloc if init. size ( ) > N .

Example

Run this code 
#include <cassert>
#include <initializer_list>
#include <inplace_vector>
#include <new>
#include <print>
#include <ranges>
 
int main()
{
    std::inplace_vector<int, 4> v1; // overload (1)
    assert(v1.size() == 0 && v1.capacity() == 4);
 
    std::inplace_vector<int, 0> v2; // overload (1), N == 0 is allowed
    assert(v2.size() == 0 && v2.capacity() == 0);
 
    std::inplace_vector<int, 5> v3(3); // overload (2)
    assert(v3.size() == 3 && v3.capacity() == 5);
    std::println("v3 = {}", v3);
 
    try
    {
        std::inplace_vector<int, 3> v(4); // overload (2), throws: count > N
    }
    catch(const std::bad_alloc& ex1)
    {
        std::println("ex1.what(): {}", ex1.what());
    }
 
    std::inplace_vector<int, 5> v4(3, 8); // overload (3)
    assert(v4.size() == 3 && v4.capacity() == 5);
    std::println("v4 = {}", v4);
 
    try
    {
        std::inplace_vector<int, 3> v(4, 2); // overload (3), throws: count > N
    }
    catch(const std::bad_alloc& ex2)
    {
        std::println("ex2.what(): {}", ex2.what());
    }
 
    const auto init = {1, 2, 3};
 
    std::inplace_vector<int, 4> v5(init.begin(), init.end()); // overload (4)
    assert(v5.size() == 3 && v5.capacity() == 4);
    std::println("v5 = {}", v5);
 
    std::inplace_vector<int, 4> v6(std::from_range, init); // overload (5)
    assert(v6.size() == 3 && v6.capacity() == 4);
    std::println("v6 = {}", v6);
 
    std::inplace_vector<int, 4> v7(v6); // overload (6)
    assert(v7.size() == 3 && v7.capacity() == 4);
    std::println("v7 = {}", v7);
    assert(v6.size() == 3);
 
    std::inplace_vector<int, 4> v8(std::move(v6)); // overload (7)
    // Note that after the move v6 is left in valid but indeterminate state.
    assert(v8.size() == 3 && v8.capacity() == 4);
    std::println("v8 = {}", v8);
 
    std::inplace_vector<int, 4> v9(init); // overload (8)
    assert(v9.size() == 3 && v9.capacity() == 4);
    std::println("v9 = {}", v9);
 
    try
    {
        std::inplace_vector<int, 2> v(init); // overload (8), throws: init.size() > N
    }
    catch(const std::bad_alloc& ex3)
    {
        std::println("ex3.what(): {}", ex3.what());
    }
}

Possible output: 

v3 = [0, 0, 0]
ex1.what(): std::bad_alloc
v4 = [42, 42, 42]
ex2.what(): std::bad_alloc
v5 = [1, 2, 3]
v6 = [1, 2, 3]
v7 = [1, 2, 3]
v8 = [1, 2, 3]
v9 = [1, 2, 3]
ex3.what(): std::bad_alloc

See also

assigns values to the container
(public member function)
[static]
returns the number of elements that can be held in currently allocated storage
(public static member function)
direct access to the underlying contiguous storage
(public member function)
returns the number of elements
(public member function)
(C++17) (C++20)
returns the size of a container or array
(function template)
(C++17)
obtains the pointer to the underlying array
(function template)
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