std::span::last(3) | C++ Standard Libary | std::span::last(3) |
NAME¶
std::span::last - std::span::last
Synopsis¶
template< std::size_t Count >
constexpr std::span<element_type, Count> last() const;
constexpr std::span<element_type, std::dynamic_extent> last( size_type
Count )
const;
Obtains a span that is a view over the last Count elements of this span. The
program
is ill-formed if Count > Extent. The behavior is undefined if Count >
size().
Return value¶
A span r that is a view over the last Count elements of *this,
such that r.data() ==
this->data() + (this->size() - Count) && r.size() == Count.
Example¶
// Run this code
#include <iostream>
#include <span>
#include <string_view>
auto print = [](std::string_view const title, auto const& container) {
std::cout << title << "[" << std::size(container)
<< "]{ ";
for (auto const& elem : container)
std::cout << elem << ", ";
std::cout << "};\n";
};
void run(std::span<const int> span)
{
print("span: ", span);
std::span<const int, 3> span_last = span.last<3>();
print("span.last<3>(): ", span_last);
std::span<const int, std::dynamic_extent> span_last_dynamic =
span.last(2);
print("span.last(2): ", span_last_dynamic);
}
int main()
{
int a[8]{ 1, 2, 3, 4, 5, 6, 7, 8, };
print("int a", a);
run(a);
}
Output:¶
int a[8]{ 1, 2, 3, 4, 5, 6, 7, 8, };
span: [8]{ 1, 2, 3, 4, 5, 6, 7, 8, };
span.last<3>(): [3]{ 6, 7, 8, };
span.last(2): [2]{ 7, 8, };
See also¶
first obtains a subspan consisting of the first N elements of the
sequence
(public member function)
subspan obtains a subspan
(public member function)
2022.07.31 | http://cppreference.com |