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std::deque::deque(3) C++ Standard Libary std::deque::deque(3) NAME std::deque::deque - std::deque::deque Synopsis deque(); (1) explicit deque( const Allocator& alloc ); (2) explicit deque( size_type count, const T& value = T(), (until C++11) const Allocator& alloc = Allocator() ); deque( size_type count, const T& value, (since C++11) const Allocator& alloc = Allocator() ); explicit deque( size_type count ); (since C++11) (un- til C++14) explicit deque( size_type count, const Allocator& alloc = (since C++14) Allocator() ); template< class InputIt > (3) deque( InputIt first, InputIt last, (5) const Allocator& alloc = Allocator() ); deque( const deque& other ); (4) (6) deque( const deque& other, const Allocator& (7) (since C++11) alloc ); deque( deque&& other ); (8) (since C++11) deque( deque&& other, const Allocator& alloc ); (9) (since C++11) deque( std::initializer_list<T> init, (10) (since C++11) const Allocator& alloc = Allocator() ); template< container-compatible-range<T> R > deque( std::from_range_t, R&& rg, (11) (since C++23) const Allocator& alloc = Allocator() ); Constructs a new container from a variety of data sources, option- ally using a user supplied allocator alloc. 1) Default constructor. Constructs an empty container with a de- fault-constructed allocator. 2) Constructs an empty container with the given allocator alloc. 3) Constructs the container with count copies of elements with value value. 4) Constructs the container with count default-inserted instances of T. No copies are made. 5) Constructs the container with the contents of the range [first, last). This constructor has the same effect as deque(static_cast<size_type>(first), static_cast<value_type>(last), a) (until C++11) if InputIt is an integral type. This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator, to avoid ambiguity with the overload (since C++11) (3). 6) Copy constructor. Constructs the container with the copy of the contents of other. The allocator is obtained as if by calling (since std::allocator_traits<allocator_type>::select_on_container_copy_con- struction( C++11) other.get_allocator()). 7) Constructs the container with the copy of the contents of other, using alloc as the allocator. During class template argument deduction, only the first argument contributes to the deduction of the container's Allocator template (since C++23) parameter. 8) Move constructor. Constructs the container with the contents of other using move semantics. Allocator is obtained by move-construction from the allo- cator belonging to other. 9) Allocator-extended move constructor. Using alloc as the allocator for the new container, moving the contents from other; if alloc != other.get_al- locator(), this results in an element-wise move. During class template argument deduction, only the first argument contributes to the deduction of the container's Allocator template (since C++23) parameter. 10) Constructs the container with the contents of the initializer list init. 11) Constructs the container with the contents of the range rg. 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 [first, last) 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 rg - a container compatible range, that is, an input_range whose elements are convertible to T Complexity 1,2) Constant. 3,4) Linear in count. 5) Linear in distance between first and last. 6,7) Linear in size of other. 8) Constant. 9) Linear if alloc != other.get_allocator(), otherwise constant. 10) Linear in size of init. 11) Linear in ranges::distance(rg). Exceptions Calls to Allocator::allocate may throw. Notes After container move construction (overload (8)), references, point- ers, and iterators (other than the end iterator) to other remain valid, but refer to elements that are now in *this. The current standard makes this guarantee via the blanket statement in [container.reqmts]/67, and a more direct guarantee is under consideration via LWG issue 2321. Feature-test macro Value Std Feature __cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construc- tion and insertion; overload (11) Example // Run this code #include <iostream> #include <string> #include <deque> template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<T>& v) { s.put('{'); for (char comma[]{'\0', ' ', '\0'}; const auto& e : v) s << comma << e, comma[0] = ','; return s << "}\n"; } int main() { // C++11 initializer list syntax: std::deque<std::string> words1{"the", "frogurt", "is", "also", "cursed"}; std::cout << "1: " << words1; // words2 == words1 std::deque<std::string> words2(words1.begin(), words1.end()); std::cout << "2: " << words2; // words3 == words1 std::deque<std::string> words3(words1); std::cout << "3: " << words3; // words4 is {"Mo", "Mo", "Mo", "Mo", "Mo"} std::deque<std::string> words4(5, "Mo"); std::cout << "4: " << words4; auto const rg = {"cat", "cow", "crow"}; #ifdef __cpp_lib_containers_ranges std::deque<std::string> words5(std::from_range, rg); // overload (11) #else std::deque<std::string> words5(rg.begin(), rg.end()); // overload (5) #endif std::cout << "5: " << words5; } Output: 1: {the, frogurt, is, also, cursed} 2: {the, frogurt, is, also, cursed} 3: {the, frogurt, is, also, cursed} 4: {Mo, Mo, Mo, Mo, Mo} 5: {cat, cow, crow} Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior the complexity requirement of LWG 144 C++98 overload (5) was the same changed to linear complexity as that of the corresponding overload of std::vector the complexity requirement of changed to linear in LWG 237 C++98 overload std::dis- tance(first, last) (5) was linear in first - last for overload (4), the elements in LWG 868 C++98 the container were default they are value-initialized constructed LWG 2193 C++11 the default constructor is explicit made non-ex- plicit See also assign assigns values to the container (public member function) operator= assigns values to the container (public member function) http://cppreference.com 2024.06.10 std::deque::deque(3)
NAME | Synopsis | Parameters | Complexity | Exceptions | Notes | Example | Output: | See also
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