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

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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)
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span::empty
span::size
span::size_bytes
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span::first
span::last
span::subspan
Non-member functions
as_bytesas_writable_bytes
Non-member constant
dynamic_extent
Deduction guides

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constexpr reference back()const;		(since C++20)

Returns a reference to the last element in the span.

Ifempty() istrue, the behavior is undefined.

(until C++26)

Ifempty() istrue:

If the implementation ishardened, acontract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined.
If the implementation is not hardened, the behavior is undefined.

(since C++26)

[edit]Return value

A reference to the back element.

[edit]Complexity

Constant.

[edit]Notes

For a spanc, the expressionc.back() is equivalent to*(c.end()-1).

[edit]Example

Run this code

#include <iostream>#include <span> void print_forward(conststd::span<constint> span){for(auto n{span.size()}; n!=0;--n)std::cout<< span.last(n).front()<<' ';std::cout<<'\n';} void print_backward(conststd::span<constint> span){for(auto n{span.size()}; n!=0;--n)std::cout<< span.first(n).back()<<' ';std::cout<<'\n';} int main(){constexprint numbers[]{0,1,2,3,4};    print_forward(numbers);    print_backward(numbers);}