std::span<T,Extent>::begin, std::span<T,Extent>::cbegin
constexpr iterator begin() const noexcept; | (1) | (since C++20) |
constexpr const_iterator cbegin() const noexcept; | (2) | (since C++23) |
Returns an iterator to the first element of the span.
If the span is empty, the returned iterator will be equal to end().
Return value
Iterator to the first element.
Complexity
Constant.
Example
#include <iostream>
#include <span>
void print(std::span<const int> array)
{
std::cout << "array = ";
for (auto it = array.begin(); it != array.end(); ++it)
std::cout << *it << ' ';
std::cout << '\n';
}
void set_first_element(std::span<int> sp, int new_value)
{
if (!sp.empty())
{
std::cout << "old *begin = " << *sp.begin() << '\n';
*sp.begin() = new_value;
std::cout << "new *begin = " << *sp.begin() << '\n';
}
}
int main()
{
int array[]{1, 3, 4, 5};
print(array);
set_first_element(array, 2);
print(array);
}
Output:
array = 1 3 4 5 old *begin = 1 new *begin = 2 array = 2 3 4 5
See also
|
(C++23) | 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) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/cpp/container/span/begin
