std::toupper(std::locale)

Defined in header `<locale>`
template< class CharT > CharT toupper( CharT ch, const locale& loc );

Converts the character ch to uppercase if possible, using the conversion rules specified by the given locale's std::ctype facet.

Parameters

ch	-	character
loc	-	locale

Return value

Returns the uppercase form of ch if one is listed in the locale, otherwise returns ch unchanged.

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::toupper.

Possible implementation

template< class CharT >
CharT toupper( CharT ch, const std::locale& loc ) {
    return std::use_facet<std::ctype<CharT>>(loc).toupper(ch);
}

Example

Run this code

#include <iostream>
#include <cwctype>
#include <locale>
 
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, toupper(" << (std::wint_t)c << ") = "
              << (std::wint_t)std::toupper(c, std::locale()) << '\n';
 
    std::cout << "in Unicode locale, toupper(" << (std::wint_t)c << ") = "
              << (std::wint_t)std::toupper(c, std::locale("en_US.utf8")) << '\n';
}

Possible output:

in the default locale, toupper(0x17f) = 0x17f
in Unicode locale, toupper(0x17f) = 0x53

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Technical specifications
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External libraries

tolower(std::locale)	converts a character to lowercase using the ctype facet of a locale (function template)
toupper	converts a character to uppercase (function)
towupper	converts a wide character to uppercase (function)