(C++17) | ||||
| Sequence | ||||
(C++11) | ||||
(C++26) | ||||
(C++26) | ||||
(C++11) | ||||
| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Adaptors | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
| Views | ||||
(C++20) | ||||
(C++23) | ||||
| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
| Member functions | ||||
| Element access | ||||
span::at (C++26) | ||||
| Iterators | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
| Observers | ||||
| Subviews | ||||
| Non-member functions | ||||
| Non-member constant | ||||
| Deduction guides |
constexpr reference at( size_type pos)const; | (since C++26) | |
Returns a reference to the element at specified locationpos, with bounds checking.
Ifpos is not within the range of the span, an exception of typestd::out_of_range is thrown.
Contents |
| pos | - | position of the element to return |
Reference to the requested element.
std::out_of_range ifpos>= size().
Constant.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_span | 202311L | (C++26) | std::span::at |
#include <chrono>#include <cstddef>#include <iostream>#include <span>#include <stdexcept> int main(){int x[]{1,2,4,5,5,6};std::span data(x); // Set element 1 data.at(1)=88; // Read element 2std::cout<<"Element at index 2 has value "<< data.at(2)<<'\n'; std::cout<<"data size = "<< data.size()<<'\n'; try{// Try to set an element at random position >= size()auto moon_phase=[]{returnstd::chrono::system_clock::now().time_since_epoch().count()%8;}; data.at(data.size()+ moon_phase())=13;}catch(conststd::out_of_range& ex){std::cout<< ex.what()<<'\n';} // Print final valuesstd::cout<<"data:";for(int elem: data)std::cout<<' '<< elem;std::cout<<'\n';}
Possible output:
Element at index 2 has value 4data size = 6std::out_of_range: pos (which is 8) >= size() (which is 6)data: 1 88 4 5 5 6
| access specified element (public member function)[edit] |
