std::vector::vector

(1)
explicit vector( const Allocator& alloc = Allocator() );
(until C++14)
vector() : vector( Allocator() ) {}
explicit vector( const Allocator& alloc );
(since C++14)
(2)
explicit vector( size_type count, 
                 const T& value = T(),
                 const Allocator& alloc = Allocator());
(until C++11)
         vector( size_type count, 
                 const T& value,
                 const Allocator& alloc = Allocator());
(since C++11)
(3)
explicit vector( size_type count );
(since C++11)
(until C++14)
explicit vector( size_type count, const Allocator& alloc = Allocator() );
(since C++14)
template< class InputIt >
vector( InputIt first, InputIt last, 
        const Allocator& alloc = Allocator() );
(4)
vector( const vector& other );
(5)
vector( const vector& other, const Allocator& alloc );
(5) (since C++11)
vector( vector&& other )
(6) (since C++11)
vector( vector&& other, const Allocator& alloc );
(6) (since C++11)
vector( std::initializer_list<T> init, 
        const Allocator& alloc = Allocator() );
(7) (since C++11)

Constructs a new container from a variety of data sources, optionally using a user supplied allocator alloc.

1) Default constructor. Constructs an empty container.
2) Constructs the container with count copies of elements with value value.
3) Constructs the container with count default-inserted instances of T. No copies are made.
4) Constructs the container with the contents of the range [first, last).
This constructor has the same effect as overload (2) if InputIt is an integral type. (until C++11)
This overload only participates in overload resolution if InputIt satisfies InputIterator , to avoid ambiguity with the overload (2). (since C++11)
5) Copy constructor. Constructs the container with the copy of the contents of other. If alloc is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::select_on_container_copy_construction(other.get_allocator().
6) Move constructor. Constructs the container with the contents of other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other.
7) Constructs the container with the contents of the initializer list init.

Parameters

alloc - allocator to use for all memory allocations of this container
count - the size of the container
value - the value to initialize elements of the container with
first, last - the range to copy the elements from
other - another container to be used as source to initialize the elements of the container with
init - initializer list to initialize the elements of the container with

Complexity

1) Constant
2-3) Linear in count
4) Linear in distance between first and last
5) Linear in size of other
6) Constant. If alloc is given and alloc != other.get_allocator(), then linear.
7) Linear in size of init

Notes

The overload (3) zeroes out elements of non-class types such as int, which is different from the behavior of new[] , which leaves them uninitialized. To match the behavior of new[], a custom Allocator::construct can be provided which leaves such elements uninitialized.

Exceptions

1)
noexcept specification:
noexcept(noexcept(Allocator()))
6)
noexcept specification:
noexcept
(since C++17)

Example

#include <vector>
#include <string>
#include <iostream>
 
template<typename T>
std::ostream& operator<<(std::ostream& s, const std::vector<T>& v) {
    s.put('[');
    char comma[3] = {'\0', ' ', '\0'};
    for (const auto& e : v) {
        s << comma << e;
        comma[0] = ',';
    }
    return s << ']';
}
 
int main() 
{
    // c++11 initializer list syntax:
    std::vector<std::string> words1 {"the", "frogurt", "is", "also", "cursed"};
    std::cout << "words1: " << words1 << '\n';
 
    // words2 == words1
    std::vector<std::string> words2(words1.begin(), words1.end());
    std::cout << "words2: " << words2 << '\n';
 
    // words3 == words1
    std::vector<std::string> words3(words1);
    std::cout << "words3: " << words3 << '\n';
 
    // words4 is {"Mo", "Mo", "Mo", "Mo", "Mo"}
    std::vector<std::string> words4(5, "Mo");
    std::cout << "words4: " << words4 << '\n';
}

Output:

words1: [the, frogurt, is, also, cursed]
words2: [the, frogurt, is, also, cursed]
words3: [the, frogurt, is, also, cursed]
words4: [Mo, Mo, Mo, Mo, Mo]

See also

assigns values to the container
(public member function)
operator=
assigns values to the container
(public member function)
doc_CPP
2016-10-11 10:08:21
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