template<class T>
size_type find_first_of(const T& t, size_type pos = 0) const;
size_type find_first_of(const basic_string& str, size_type pos = 0) const noexcept;
size_type find_first_of(const charT* s, size_type pos, size_type n) const;
size_type find_first_of(const charT* s, size_type pos = 0) const;
size_type find_first_of(charT c, size_type pos = 0) const;