std::span<T,Extent>::last

 

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std::span

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span::beginspan::cbegin (C++20)(C++23)

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as_bytesas_writable_bytes (C++20)(C++20)

Non-member constant

dynamic_extent (C++20)

Deduction guides(C++20)

 

template< std::size_t Count > constexpr std::span<element_type, Count>     last() const;	(1)	(since C++20)
constexpr std::span<element_type, std::dynamic_extent>     last( size_type Count ) const;	(2)	(since C++20)

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 (C++20)	obtains a subspan consisting of the first N elements of the sequence (public member function)
subspan (C++20)	obtains a subspan (public member function)