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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
	  reference at(	size_type pos );			(until C++20)
	  constexpr reference at( size_type pos	);		(since C++20)
	  const_reference at( size_type	pos ) const;		(until C++20)
	  constexpr const_reference at(	size_type pos )	const;	(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 in-
       valid 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().

Complexity
	  Constant.

Example
       // Run this code

	#include <stdexcept>
	#include <iostream>
	#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

See also
	  operator[] accesses the specified character
		     (public member function)
	  at	     accesses the specified character with bounds checking
	  (C++17)	  (public      member	  function     of     std::ba-
       sic_string_view<CharT,Traits>)

http://cppreference.com		  2022.07.31	      std::basic_string::at(3)

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