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std::array(3) C++ Standard Libary std::array(3) NAME std::array - std::array Synopsis Defined in header <array> template< class T, (since C++11) std::size_t N > struct array; std::array is a container that encapsulates fixed size arrays. This container is an aggregate type with the same semantics as a struct holding a C-style array T[N] as its only non-static data member. Unlike a C- style array, it doesn't decay to T* automatically. As an aggregate type, it can be initialized with aggregate-initialization given at most N initializers that are con- vertible to T: std::array<int, 3> a = {1,2,3};. The struct combines the performance and accessibility of a C-style array with the benefits of a standard container, such as knowing its own size, sup- porting assignment, random access iterators, etc. std::array satisfies the requirements of Container and Reversible- Container except that default-constructed array is not empty and that the complexity of swapping is linear, satisfies the requirements of ContiguousContainer, (since C++17) and partially satisfies the requirements of Sequence- Container. There is a special case for a zero-length array (N == 0). In that case, array.begin() == array.end(), which is some unique value. The effect of calling front() or back() on a zero-sized array is undefined. An array can also be used as a tuple of N elements of the same type. Iterator invalidation As a rule, iterators to an array are never invalidated throughout the lifetime of the array. One should take note, however, that during swap, the it- erator will continue to point to the same array element, and will thus change its value. Member types Member type Definition value_type T size_type std::size_t difference_type std::ptrdiff_t reference value_type& const_reference const value_type& pointer value_type* const_pointer const value_type* LegacyRandomAccessIterator and (until C++17) LegacyContiguousIterator to value_type LegacyRandomAccessIterator and (since C++17) iterator LegacyContiguousIterator that is a Literal- Type (until C++20) to value_type LegacyRandomAccessIterator, contiguous_iterator, and ConstexprIterator to (since C++20) value_type LegacyRandomAccessIterator and (until C++17) LegacyContiguousIterator to const value_type LegacyRandomAccessIterator and (since C++17) const_iterator LegacyContiguousIterator that is a Literal- Type (until C++20) to const value_type LegacyRandomAccessIterator, contiguous_iterator, and ConstexprIterator to (since C++20) const value_type reverse_iterator std::reverse_iterator<iterator> const_reverse_iterator std::reverse_iterator<const_iterator> Member functions Implicitly-defined member functions initializes the array following the rules of aggregate constructor initialization (note that default initializa- tion may result in (implicitly declared) indeterminate values for non-class T) (public member function) destructor destroys every element of the array (implicitly declared) (public member function) operator= overwrites every element of the array with the corresponding (implicitly declared) element of another array (public member function) Element access at access specified element with bounds checking (C++11) (public member function) operator[] access specified element (C++11) (public member function) front access the first element (C++11) (public member function) back access the last element (C++11) (public member function) data direct access to the underlying array (C++11) (public member function) Iterators begin returns an iterator to the beginning cbegin (public member function) (C++11) end returns an iterator to the end cend (public member function) (C++11) rbegin returns a reverse iterator to the beginning crbegin (public member function) (C++11) rend returns a reverse iterator to the end crend (public member function) (C++11) Capacity empty checks whether the container is empty (C++11) (public member function) size returns the number of elements (C++11) (public member function) max_size returns the maximum possible number of ele- ments (C++11) (public member function) Operations fill fill the container with specified value (C++11) (public member function) swap swaps the contents (C++11) (public member function) Non-member functions operator== operator!= operator< operator<= operator> operator>= lexicographically compares the values in the array operator<=> (function template) (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (C++20) std::get(std::array) accesses an element of an array (C++11) (function template) std::swap(std::array) specializes the std::swap algorithm (C++11) (function template) to_array creates a std::array object from a built-in array (C++20) (function template) Helper classes std::tuple_size<std::array> obtains the size of an array (C++11) (class template specialization) std::tuple_element<std::array> obtains the type of the elements of array (C++11) (class template specialization) Deduction guides(since C++17) Example // Run this code #include <string> #include <iterator> #include <iostream> #include <algorithm> #include <array> int main() { // construction uses aggregate initialization std::array<int, 3> a1{ {1, 2, 3} }; // double-braces required in C++11 prior to // the CWG 1270 revision (not needed in C++11 // after the revision and in C++14 and beyond) std::array<int, 3> a2 = {1, 2, 3}; // double braces never re- quired after = std::array<std::string, 2> a3 = { std::string("a"), "b" }; // container operations are supported std::sort(a1.begin(), a1.end()); std::reverse_copy(a2.begin(), a2.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << '\n'; // ranged for loop is supported for(const auto& s: a3) std::cout << s << ' '; // deduction guide for array creation (since C++17) [[maybe_unused]] std::array a4{3.0, 1.0, 4.0}; // -> std::ar- ray<double, 3> } Output: 3 2 1 a b See also make_array Creates a std::array object whose size and optionally (library fundamentals TS v2) element type are deduced from the argu- ments (function template) http://cppreference.com 2022.07.31 std::array(3)
NAME | Synopsis | Member types | Member functions | Implicitly-defined member functions | Element access | Iterators | Capacity | Operations | Non-member functions | Helper classes | Example | Output: | See also
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