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

NAME
       std::basic_string::resize - std::basic_string::resize

Synopsis
	  void	resize(	 size_type  count  );		 (1)  (constexpr since
       C++20)
	  void resize( size_type count,	 CharT	ch  );	(2)  (constexpr	 since
       C++20)

	  Resizes the string to	contain	count characters.

	  If  the  current  size is less than count, additional	characters are
       appended:

	  1) Initializes appended characters to	 CharT()  ('\0'	 if  CharT  is
       char).
	  2) Initializes appended characters to	ch.

	  If  the current size is greater than count, the string is reduced to
       its first count
	  elements.

Parameters
	  count	- new size of the string
	  ch	- character to initialize the new characters with

Return value
	  (none)

Exceptions
	  std::length_error if count > max_size(). Any	exceptions  thrown  by
       corresponding
	  Allocator.

	  If  an  exception is thrown for any reason, this function has	no ef-
       fect (strong
	  exception safety guarantee).

Example
       // Run this code

	#include <iomanip>
	#include <iostream>
	#include <stdexcept>

	int main()
	{
	    const unsigned desired_length{8};
	    std::string	long_string("Where is the end?");
	    std::string	short_string("H");

	    std::cout << "Basic	functionality:\n"
		      << "Shorten:\n"
		      << "1. Before: " << std::quoted(long_string) << '\n';
	    long_string.resize(desired_length);
	    std::cout << "2. After:  " << std::quoted(long_string) << '\n';

	    std::cout << "Lengthen with	a given	value 'a':\n"
		      << "3. Before: " << std::quoted(short_string) << '\n';
	    short_string.resize(desired_length,	'a');
	    std::cout << "4. After:  " << std::quoted(short_string) << '\n';

	    std::cout	<<   "Lengthen	 with	char()	 ==    "    <<	  sta-
       tic_cast<int>(char()) <<	'\n'
		      << "5. Before: " << std::quoted(short_string) << '\n';
	    short_string.resize(desired_length + 3);
	    std::cout << "6. After:  \"";
	    for	(char c	: short_string)
		std::cout << (c	== char() ? '@'	: c);
	    std::cout << "\"\n\n";

	    std::cout << "Errors:\n";
	    std::string	s;

	    try
	    {
		// size	is OK, no length_error
		// (may	throw bad_alloc)
		s.resize(s.max_size() -	1, 'x');
	    }
	    catch (const std::bad_alloc& ex)
	    {
		std::cout << "1. Exception: " << ex.what() << '\n';
	    }

	    try
	    {
		// size	is OK, no length_error
		// (may	throw bad_alloc)
		s.resize(s.max_size(), 'x');
	    }
	    catch (const std::bad_alloc& ex)
	    {
		std::cout << "2. Exception: " << ex.what() << '\n';
	    }

	    try
	    {
		// size	is BAD,	throw length_error
		s.resize(s.max_size() +	1, 'x');
	    }
	    catch (const std::length_error& ex)
	    {
		std::cout << "3. Length	error: " << ex.what() << '\n';
	    }
	}

Possible output:
	Basic functionality:
	Shorten:
	1. Before: "Where is the end?"
	2. After:  "Where is"
	Lengthen with a	given value 'a':
	3. Before: "H"
	4. After:  "Haaaaaaa"
	Lengthen with char() ==	0
	5. Before: "Haaaaaaa"
	6. After:  "Haaaaaaa@@@"

	Errors:
	1. Exception: std::bad_alloc
	2. Exception: std::bad_alloc
	3. Length error: basic_string::_M_replace_aux

	  Defect reports

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

	    DR	  Applied to	    Behavior as	published	       Correct
       behavior
	  LWG  847 C++98      there was	no exception safety	  added	strong
       exception safety
			     guarantee				 guarantee

See also
	  size		returns	the number of characters
	  length	(public	member function)
	  reserve	reserves storage
			(public	member function)
	  shrink_to_fit	reduces	memory usage by	freeing	unused memory
	  (DR*)		(public	member function)

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

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