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

Returns a reference to the character at specified location pos . Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.

Parameters

Return value

Reference to the requested character.

Exceptions

Throws std::out_of_range if pos >= size ( ) .

If an exception is thrown for any reason, these functions have no effect ( strong exception safety guarantee ).

Complexity

Constant.

Example

#include <iostream>
#include <stdexcept>
#include <string>
 
int main()
{
    std::string s("message"); // for capacity
 
    s = "abc";
    s.at(2) = 'x'; // OK
    std::cout << s << '\n';
 
    std::cout << "string size = " << s.size() << '\n';
    std::cout << "string capacity = " << s.capacity() << '\n';
 
    try
    {
        // This will throw since the requested offset is greater than the current size.
        s.at(3) = 'x';
    }
    catch (std::out_of_range const& exc)
    {
        std::cout << exc.what() << '\n';
    }
}

abx
string size = 3
string capacity = 7
basic_string::at

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also