std::towupper(3)

NAME
std::towupper - std::towupper

Synopsis
   Defined in header <cwctype>
   std::wint_t towupper( std::wint_t ch );
   Converts the given wide character to uppercase, if possible.
   If the value of ch is neither representable as a wchar_t nor equal to the value of
   the macro WEOF, the behavior is undefined.

Parameters
   ch - wide character to be converted

Return value
   Uppercase version of ch or unmodified ch if no uppercase version is listed in the
   current C locale.

Notes
   Only 1:1 character mapping can be performed by this function, e.g. the uppercase
   form of 'ß' is (with some exceptions) the two-character string "SS", which cannot be
   obtained by std::towupper.
   ISO 30112 specifies which pairs of Unicode characters are included in this mapping.

Example
   The latin letter 'ſ' (U+017F) is the alternative lowercase form of 'S' (U+0053). // Run this code
 #include <clocale>
 #include <cwctype>
 #include <iostream>
 int main()
 {
     wchar_t c = L'\u017f'; // Latin small letter Long S ('ſ')
     std::cout << std::hex << std::showbase;
     std::cout << "in the default locale, towupper("
               << static_cast<std::wint_t>(c) << ") = "
               << std::towupper(c) << '\n';
     std::setlocale(LC_ALL, "en_US.utf8");
     std::cout << "in Unicode locale, towupper("
               << static_cast<std::wint_t>(c) << ") = "
               << std::towupper(c) << '\n';
 }

Output:
 in the default locale, towupper(0x17f) = 0x17f
 in Unicode locale, towupper(0x17f) = 0x53

See also
   towlower converts a wide character to lowercase
                        (function)
                        converts a character to uppercase using the ctype facet of a
   toupper(std::locale) locale
                        (function template)
   toupper converts a character to uppercase
                        (function)
   C documentation for
   towupper