f_format         1303 complex.c          return f_format(self, rb_String);
f_format         1324 complex.c          rb_str_concat(s, f_format(self, rb_inspect));
f_format         1617 rational.c         return f_format(self, f_to_s);
f_format         1636 rational.c         rb_str_concat(s, f_format(self, f_inspect));