std::collate
| Defined in header <locale>
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| template< class CharT > class collate; |
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Class std::collate encapsulates locale-specific collation (comparison) and hashing of strings. This facet is used by std::basic_regex and can be applied, by means of std::locale::operator(), directly to all standard algorithms that expect a string comparison predicate.
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 implements its own (locale-specific) versions of these specializations.
Member types
| Member type | Definition |
char_type
|
CharT
|
string_type
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std::basic_string<CharT>
|
Member functions
| constructs a new collate facet (public member function) | |
| destructs a collate facet (protected member function) | |
invokes do_compare (public member function) | |
invokes do_transform (public member function) | |
invokes do_hash (public member function) |
Member objects
| static std::locale::id id |
id of the locale (public member object) |
Protected member functions
| [virtual] |
compares two strings using this facet's collation rules (virtual protected member function) |
| [virtual] |
transforms a string so that collation can be replaced by comparison (virtual protected member function) |
| [virtual] |
generates an integer hash value using this facet's collation rules (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 förnamn zebra ängel år ögrupp English locale collation order: ängel ar år förnamn ögrupp zebra Zebra Swedish locale collation order: ar förnamn zebra Zebra år ängel ögrupp
See also
| lexicographically compares two strings using this locale's collate facet (public member function of std::locale) | |
| creates a collate facet for the named locale (class template) |