std::array
Defined in header
<array>
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template<
class T, |
(since C++11) | |
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 convertible 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, supporting assignment, random access iterators, etc.
std::array
satisfies the requirements of Container
and ReversibleContainer
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 SequenceContainer
.
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.
Contents |
[edit] 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 iterator will continue to point to the same array element, and will thus change its value.
[edit] Member types
Member type | Definition |
value_type
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T
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size_type
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std::size_t |
difference_type
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std::ptrdiff_t |
reference
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value_type&
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const_reference
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const value_type&
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pointer
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value_type*
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const_pointer
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const value_type*
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iterator
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RandomAccessIterator and LiteralType (since C++17)
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const_iterator
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Constant random access iterator and LiteralType (since C++17)
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reverse_iterator
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std::reverse_iterator<iterator> |
const_reverse_iterator
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std::reverse_iterator<const_iterator> |
[edit] Member functions
Implicitly-defined member functions |
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initialized the array following the rules of aggregate initialization (note that default initialization may result in indeterminate values for non-class T ) (public member function) |
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destroys every element of the array (public member function) |
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overwrites every element of the array with the corresponding element of another array (public member function) |
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Element access |
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access specified element with bounds checking (public member function) |
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access specified element (public member function) |
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access the first element (public member function) |
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access the last element (public member function) |
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direct access to the underlying array (public member function) |
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Iterators |
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returns an iterator to the beginning (public member function) |
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returns an iterator to the end (public member function) |
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returns a reverse iterator to the beginning (public member function) |
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returns a reverse iterator to the end (public member function) |
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Capacity |
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checks whether the container is empty (public member function) |
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returns the number of elements (public member function) |
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returns the maximum possible number of elements (public member function) |
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Operations |
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fill the container with specified value (public member function) |
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swaps the contents (public member function) |
[edit] Non-member functions
lexicographically compares the values in the array (function template) |
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accesses an element of an array (function template) |
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(C++11)
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specializes the std::swap algorithm (function template) |
[edit] Helper classes
obtains the size of an array (class template specialization) |
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obtains the type of the elements of array (class template specialization) |
[edit] Example
#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 (not in C++14) std::array<int, 3> a2 = {1, 2, 3}; // never required 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 << ' '; }
Output:
3 2 1 a b
[edit] See also
Creates a std::array object whose size and optionally element type are deduced from the arguments (function template) |
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Creates a std::array object from a built-in array (function template) |