nt;                                           // number of reported errors
     ErrorStream();                                       // constructor
     void StoreError(int n, int line, int col, String s); // report/store an error
     void ParsErr(int n, int line, int col);              // record syntax error
     void SemErr(int n, int line, int col);               // record semantic error
     void Exception(String s);                            // report S and abort
     void Summarize(String s);       