std::ctype::tolower,std::ctype::do_tolower(3)

NAME
std::ctype::tolower,std::ctype::do_tolower - std::ctype::tolower,std::ctype::do_tolower

Synopsis
   Defined in header <locale>
   public: (1)
   CharT tolower( CharT c ) const;
   public: (2)
   const CharT* tolower( CharT* beg, const CharT* end ) const;
   protected: (3)
   virtual CharT do_tolower( CharT c ) const;
   protected: (4)
   virtual const CharT* do_tolower( CharT* beg, const CharT* end ) const;
   1,2) Public member function, calls the protected virtual member function do_tolower
   of the most derived class.
   3) Converts the character c to lower case if a lower case form is defined by this
   locale.
   4) For every character in the character array [beg, end), for which a lower case
   form exists, replaces the character with that lower case form.

Parameters
   c - character to convert
   beg - pointer to the first character in an array of characters to convert
   end - one past the end pointer for the array of characters to convert

Return value
   1,3) Lower case character or c if no lower case form is listed by this locale.
   2,4) end

Notes
   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 do_tolower cannot be used to obtain the correct lowercase
   form in this case.

Example
// Run this code
 #include <iostream>
 #include <locale>
 void try_lower(const std::ctype<wchar_t>& f, wchar_t c)
 {
     wchar_t up = f.tolower(c);
     if (up != c)
         std::wcout << "Lower case form of \'" << c << "' is " << up << '\n';
     else
         std::wcout << '\'' << c << "' has no lower case form\n";
 }
 int main()
 {
     std::locale::global(std::locale("en_US.utf8"));
     std::wcout.imbue(std::locale());
     std::wcout << "In US English UTF-8 locale:\n";
     auto& f = std::use_facet<std::ctype<wchar_t>>(std::locale());
     try_lower(f, L'Σ');
     try_lower(f, L'Ɛ');
     try_lower(f, L'Ａ');
     std::wstring str = L"HELLo, wORLD!";
     std::wcout << "Lowercase form of the string '" << str << "' is ";
     f.tolower(&str[0], &str[0] + str.size());
     std::wcout << '\'' << str << "'\n";
 }

Output:
 In US English UTF-8 locale:
 Lower case form of 'Σ' is σ
 Lower case form of 'Ɛ' is ɛ
 Lower case form of 'Ａ' is ａ
 Lowercase form of the string 'HELLo, wORLD!' is 'hello, world!'

See also
   toupper invokes do_toupper
            (public member function)
   tolower converts a character to lowercase
            (function)
   towlower converts a wide character to lowercase
            (function)