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

NAME
       std::collate - std::collate

Synopsis
	  Defined in header <locale>
	  template< class CharT	>
	  class	collate;

	  Class	 std::collate encapsulates locale-specific collation (compari-
       son) and	hashing
	  of strings. This facet is used by std::basic_regex and  can  be  ap-
       plied, by means of
	  std::locale::operator(),  directly  to  all standard algorithms that
       expect a	string
	  comparison predicate.

	  std-collate-inheritance.svg

					  Inheritance diagram

	  Two standalone (locale-independent) specializations are provided  by
       the standard
	  library:

	  Defined in header <locale>
	  std::collate<char>	 implements  lexicographical  ordering of byte
       strings
	  std::collate<wchar_t>	implements lexicographical  ordering  of  wide
       strings

	  In addition, every locale object constructed in a C++	program	imple-
       ments its own
	  (locale-specific) versions of	these specializations.

Member types
	  Member type Definition
	  char_type   CharT
	  string_type std::basic_string<CharT>

Member functions
	  constructor	constructs a new collate facet
			(public	member function)
	  destructor	destructs a collate facet
			(protected member function)
	  compare	invokes	do_compare
			(public	member function)
	  transform	invokes	do_transform
			(public	member function)
	  hash		invokes	do_hash
			(public	member function)

Member objects
	  static std::locale::id id id of the locale
				    (public member object)

Protected member functions
	  do_compare   compares	two strings using this facet's collation rules
	  [virtual]    (virtual	protected member function)
	  do_transform	transforms  a string so	that collation can be replaced
       by comparison
	  [virtual]    (virtual	protected member function)
	  do_hash      generates an integer hash value using this facet's col-
       lation rules
	  [virtual]    (virtual	protected member function)

Example
       // Run this code

	#include <locale>
	#include <iostream>
	#include <string>
	#include <vector>
	#include <algorithm>

	int main()
	{
	    std::wcout.imbue(std::locale(""));
	    std::vector<std::wstring> v	=  {L"ar",  L"zebra",  L"\u00f6grupp",
       L"Zebra", L"\u00e4ngel",
					   L"\u00e5r", L"f\u00f6rnamn"};

	    std::wcout << "Default locale collation order: ";
	    std::sort(v.begin(), v.end());
	    for	(auto s	: v) std::wcout	<< s <<	' '; std::wcout	<< '\n';

	    std::wcout << "English locale collation order: ";
	    std::sort(v.begin(), v.end(), std::locale("en_US.UTF-8"));
	    for	(auto s	: v) std::wcout	<< s <<	' '; std::wcout	<< '\n';

	    std::wcout << "Swedish locale collation order: ";
	    std::sort(v.begin(), v.end(), std::locale("sv_SE.UTF-8"));
	    for	(auto s	: v) std::wcout	<< s <<	' '; std::wcout	<< '\n';
	}

Output:
	Default	locale collation order:	Zebra ar frnamn	zebra ngel r grupp
	English	locale collation order:	ngel ar	r frnamn grupp zebra Zebra
	Swedish	locale collation order:	ar frnamn zebra	Zebra r	ngel grupp

See also
			 lexicographically compares two	strings	using this lo-
       cale's collate
	  operator()	 facet
			 (public member	function of std::locale)
	  collate_byname creates a collate facet for the named locale
			 (class	template)

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

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