std::array<T,N>::begin, std::array<T,N>::cbegin
From cppreference.com
iterator begin() noexcept; |
(1) | (since C++11) (constexpr since C++17) |
const_iterator begin() const noexcept; |
(2) | (since C++11) (constexpr since C++17) |
const_iterator cbegin() const noexcept; |
(3) | (since C++11) (constexpr since C++17) |
Returns an iterator to the first element of the array.
If the array is empty, the returned iterator will be equal to end().
Return value
Iterator to the first element.
Complexity
Constant.
Example
Run this code
#include <algorithm>
#include <array>
#include <iomanip>
#include <iostream>
int main()
{
std::cout << std::boolalpha;
std::array<int, 0> empty;
std::cout << "1) "
<< (empty.begin() == empty.end()) << ' ' // true
<< (empty.cbegin() == empty.cend()) << '\n'; // true
// *(empty.begin()) = 42; // => undefined behavior at run-time
std::array<int, 4> numbers{5, 2, 3, 4};
std::cout << "2) "
<< (numbers.begin() == numbers.end()) << ' ' // false
<< (numbers.cbegin() == numbers.cend()) << '\n' // false
<< "3) "
<< *(numbers.begin()) << ' ' // 5
<< *(numbers.cbegin()) << '\n'; // 5
*numbers.begin() = 1;
std::cout << "4) " << *(numbers.begin()) << '\n'; // 1
// *(numbers.cbegin()) = 42; // compile-time error:
// read-only variable is not assignable
// print out all elements
std::cout << "5) ";
std::for_each(numbers.cbegin(), numbers.cend(), [](int x)
{
std::cout << x << ' ';
});
std::cout << '\n';
constexpr std::array constants{'A', 'B', 'C'};
static_assert(constants.begin() != constants.end()); // OK
static_assert(constants.cbegin() != constants.cend()); // OK
static_assert(*constants.begin() == 'A'); // OK
static_assert(*constants.cbegin() == 'A'); // OK
// *constants.begin() = 'Z'; // compile-time error:
// read-only variable is not assignable
}
Output:
1) true true
2) false false
3) 5 5
4) 1
5) 1 2 3 4
See also
| returns an iterator to the end (public member function) | |
(C++11)(C++14) |
returns an iterator to the beginning of a container or array (function template) |