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

 

C++

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Standard library

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Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

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Strings library

Containers library

Iterators library

Ranges library (C++20)

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Filesystem library (C++17)

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Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

deque

forward_list (C++11)

list

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set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

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std::span

Member functions

span::span

span::operator=

Element access

span::front

span::back

span::at (C++26)

span::operator[]

span::data

Iterators

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

span::endspan::cend (C++23)

span::rbeginspan::crbegin (C++23)

span::rendspan::crend (C++23)

Observers

span::empty

span::size

span::size_bytes

Subviews

span::first

span::last

span::subspan

Non-member functions

as_bytesas_writable_bytes

Non-member constant

dynamic_extent

Deduction guides

 

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>
 
void println(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)
{
    println("span: ", span);
 
    std::span<const int, 3> span_last = span.last<3>();
    println("span.last<3>(): ", span_last);
 
    std::span<const int, std::dynamic_extent> span_last_dynamic = span.last(2);
    println("span.last(2): ", span_last_dynamic);
}
 
int main()
{
    int a[8]{1, 2, 3, 4, 5, 6, 7, 8};
    println("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)