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| Sequence | ||||
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(C++26) | ||||
(C++26) | ||||
(C++11) | ||||
| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Adaptors | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
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| Views | ||||
(C++20) | ||||
(C++23) | ||||
| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
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| Helper classes | ||||||
| Deduction guides(C++17) | ||||||
reference at( size_type pos); | (1) | (since C++11) (constexpr since C++17) |
const_reference at( size_type pos)const; | (2) | (since C++11) (constexpr since C++14) |
Returns a reference to the element at specified locationpos, with bounds checking.
Ifpos is not within the range of the container, 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.
#include <chrono>#include <cstddef>#include <iostream>#include <array>#include <stdexcept> int main(){std::array<int,6> data{1,2,4,5,5,6}; // 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 = 6array::at: __n (which is 8) >= _Nm (which is 6)data: 1 88 4 5 5 6
| access specified element (public member function)[edit] |
