std::basic_string<CharT,Traits,Allocator>::at

	(1)
`reference at( size_type pos );`			( C++20)
`constexpr reference at( size_type pos );`			( C++20)
		(2)
`const_reference at( size_type pos ) const;`				( C++20)
`constexpr const_reference at( size_type pos ) const;`				( C++20)

pos. , std::out_of_range.

pos

,

.

std::out_of_range, pos >= size().

- , ( ).

.

#include <iostream>
#include <stdexcept>
#include <string>

int main()
{
    std::string s("message"); //  
    
    s = "abc";
    s.at(2) = 'x'; // OK
    std::cout << s << '\n';
    
    std::cout << "  = " << s.size() << '\n';
    std::cout << "  = " << s.capacity() << '\n';
    
    try
    {
        //    ,  
        //    .
        s.at(3) = 'x';
    }
    catch (std::out_of_range const& exc)
    {
        std::cout << exc.what() << '\n';
    }
}

:

abx
  = 3
  = 7
basic_string::at

C++:


LWG 847	C++98

operator[]	(public -) []
at (C++17)	(public - `std::basic_string_view<CharT,Traits>`) []







(C++20)

(C++20)
(C++11)





(C++20)


/

(C++11)
(C++11)
(C++11)
(C++17)

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std::basic_string<CharT,Traits,Allocator>::at