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CharT& operator[]( size_type pos); | (1) | (constexpr since C++20) |
const CharT& operator[]( size_type pos)const; | (2) | (constexpr since C++20) |
Returns a reference to the character at specified locationpos ifpos< size(), or ifpos== size():
The behavior is undefined. | (until C++11) |
Returns a reference toCharT(), if the object referred by the returned reference is modified to any value other thanCharT(), the behavior is undefined. | (since C++11) |
Ifpos> size() istrue, the behavior is undefined. | (until C++26) |
Ifpos> size() istrue:
| (since C++26) |
Contents |
| pos | - | position of the character to return |
Constant.
#include <iostream>#include <string> int main(){conststd::string e("Exemplar");for(unsigned i= e.length()-1; i!=0; i/=2)std::cout<< e[i];std::cout<<'\n'; constchar* c=&e[0];std::cout<< c<<'\n';// print as a C string // Change the last character of s into a 'y'std::string s("Exemplar "); s[s.size()-1]='y';// equivalent to s.back() = 'y';std::cout<< s<<'\n';}
Output:
rmxExemplarExemplary
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 259 | C++98 | overload(1) could return const lvalue data()[pos], which was ill-formed | changed to return *(begin()+ pos) |
| LWG 2475 | C++11 | ifpos== size(), the behavior of modifying the object referred by the returned reference was undefined | well-defined if modified toCharT() |
| accesses the specified character with bounds checking (public member function)[edit] | |
(DR*) | accesses the first character (public member function)[edit] |
(DR*) | accesses the last character (public member function)[edit] |
| accesses the specified character (public member function of std::basic_string_view<CharT,Traits>)[edit] |
