bool         is(mask m, charT c) const;
const charT* is(const charT* low, const charT* high,
                mask* vec) const;
const charT* scan_is(mask m,
                     const charT* low, const charT* high) const;
const charT* scan_not(mask m,
                      const charT* low, const charT* high) const;
charT        toupper(charT) const;
const charT* toupper(charT* low, const charT* high) const;
charT        tolower(charT c) const;
const charT* tolower(charT* low, const charT* high) const;
charT       widen(char c) const;
const char* widen(const char* low, const char* high, charT* to) const;
char         narrow(charT c, char dfault) const;
const charT* narrow(const charT* low, const charT* high, char dfault,
                    char* to) const;