std::basic_ios<CharT,Traits>::widen
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   char_type widen( char c ) const;  | 
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Converts a character c to its equivalent in the current locale. The result is converted from char to character type used within the stream if needed.
Effectively calls std::use_facet< std::ctype<char_type> >(getloc()).widen(c).
Parameters
| c | - | character to convert | 
Return value
Character converted to char_type
See also
|   narrows characters  (public member function)  | |
|    [virtual]  | 
  converts a character or characters from char to CharT (virtual protected member function of std::ctype<CharT>)  | 
|   widens a single-byte narrow character to wide character, if possible  (function)  |