namespace Lex {
  extern int get_next(istream &);
  extern double cur_val();
  extern const string & cur_sym();
  extern int cur_tok();
  extern const int ENDOFFILE;
  extern const int NUMBER;
  extern const int SYMBOL;
  extern const int SET_KW;
  extern const int FUN_KW;
  extern const int IF_KW;
  extern const int ELSE_KW;
  extern const int WHILE_KW;
}