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std::wcsxfrm(3)		      C++ Standard Libary	       std::wcsxfrm(3)

NAME
       std::wcsxfrm - std::wcsxfrm

Synopsis
	  Defined in header <cwchar>
	  std::size_t  wcsxfrm(	wchar_t* dest, const wchar_t* src, std::size_t
       count );

	  Transforms the null-terminated wide string pointed to	 by  src  into
       the
	  implementation-defined  form	such  that  comparing  two transformed
       strings with
	  std::wcscmp gives the	same result as comparing the original  strings
       with
	  std::wcscoll,	in the current C locale.

	  The  first count characters of the transformed string	are written to
       destination,
	  including the	terminating null character, and	the length of the full
       transformed
	  string is returned, excluding	the terminating	null character.

	  If count is 0, then dest is allowed to be a null pointer.

Notes
	  The correct length of	the buffer that	can receive the	entire	trans-
       formed string is	1
	  + std::wcsxfrm(nullptr, src, 0).

	  This	function is used when making multiple locale-dependent compar-
       isons using the
	  same wide string or set of wide strings, because it  is  more	 effi-
       cient to	use
	  std::wcsxfrm	to  transform  all  the	 strings just once, and	subse-
       quently compare the
	  transformed wide strings with	std::wcscmp.

Parameters
	  dest	- pointer to the  first	 element  of  a	 wide  null-terminated
       string to write the
		  transformed string to
	  src	 -  pointer  to	 the  null-terminated wide character string to
       transform
	  count	- maximum number of characters to output

Return value
	  The length of	the transformed	wide string, not including the	termi-
       nating
	  null-character.

Example
       // Run this code

	#include <iostream>
	#include <cwchar>

	int main()
	{
	    std::setlocale(LC_ALL, "sv_SE.utf8");

	    std::wstring in1 = L"\u00e5r";
	    std::wstring out1(1+std::wcsxfrm(nullptr, in1.c_str(), 0), L' ');
	    std::wstring in2 = L"\u00e4ngel";
	    std::wstring out2(1+std::wcsxfrm(nullptr, in2.c_str(), 0), L' ');

	    std::wcsxfrm(&out1[0], in1.c_str(),	out1.size());
	    std::wcsxfrm(&out2[0], in2.c_str(),	out2.size());

	    std::wcout << "In the Swedish locale: ";
	    if(out1 < out2)
		 std::wcout << in1 << "	before " << in2	<< '\n';
	    else
		 std::wcout << in2 << "	before " << in1	<< '\n';

	    std::wcout << "In lexicographical comparison: ";
	    if(in1 < in2)
		 std::wcout << in1 << "	before " << in2	<< '\n';
	    else
		 std::wcout << in2 << "	before " << in1	<< '\n';

	}

Output:
	In the Swedish locale: r before	ngel
	In lexicographical comparison: ngel before r

See also
		       transform  a  string  so	 that strcmp would produce the
       same result as
	  strxfrm      strcoll
		       (function)
	  do_transform transforms a string so that collation can  be  replaced
       by comparison
	  [virtual]	 (virtual   protected  member  function	 of  std::col-
       late<CharT>)
	  wcscoll      compares	two wide strings in accordance to the  current
       locale
		       (function)

http://cppreference.com		  2022.07.31		       std::wcsxfrm(3)

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