byacc

  %class byacc
  %token  A B 
  
  include <byacc.h>
  define YYPARSE yylval =
  
  %start sequence
  
  sequence : { cout << "empty\n"; }
           | A { cout << (char*) *$1 << " (b) : A\n"; } sequence 
           | B { cout << *$1 << " (b) : B\n"; } sequence 
           ;