std::towlower (3) - Linux Manuals

std::towlower: std::towlower


std::towlower - std::towlower


Defined in header <cwctype>
std::wint_t towlower( std::wint_t ch );

Converts the given wide character to lowercase, 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.


ch - wide character to be converted

Return value

Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale.


Only 1:1 character mapping can be performed by this function, e.g. the Greek uppercase letter 'Σ' has two lowercase forms, depending on the position in a word: 'σ' and 'ς'. A call to std::towlower cannot be used to obtain the correct lowercase form in this case.
ISO_30112 specifies which pairs of Unicode characters are included in this mapping.


// Run this code

  #include <iostream>
  #include <cwctype>
  #include <clocale>

  int main()
      wchar_t c = L'\u0190'; // Latin capital open E ('Ɛ')

      std::cout << std::hex << std::showbase;
      std::cout << "in the default locale, towlower(" << (std::wint_t)c << ") = "
                << std::towlower(c) << '\n';
      std::setlocale(LC_ALL, "en_US.utf8");
      std::cout << "in Unicode locale, towlower(" << (std::wint_t)c << ") = "
                << std::towlower(c) << '\n';


  in the default locale, towlower(0x190) = 0x190
  in Unicode locale, towlower(0x190) = 0x25b

See also

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