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std::basic_string::at(3)       C++ Standard Libary	std::basic_string::at(3)

NAME
     std::basic_string::at - std::basic_string::at

Synopsis
	CharT& at( size_type pos );		(1) (constexpr since C++20)
	const CharT& at( size_type pos ) const; (2) (constexpr since C++20)

	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
	pos - position of the character to return

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
     // Run this code

      #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';
	  }
      }

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

	Defect reports

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

	  DR	Applied to	  Behavior as published 	     Correct be-
     havior
	LWG 847 C++98	   there was no exception safety       added strong  ex-
     ception safety
			   guarantee			       guarantee

See also
	operator[] accesses the specified character
		   (public member function)
	at	   accesses the specified character with bounds checking
		   (public	  member	function       of	std::ba-
     sic_string_view<CharT,Traits>)

http://cppreference.com 	   2024.06.10		std::basic_string::at(3)
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