BETY::	 b BETY; EMPTY.

EMPTY::	 .

program:	  growing.

growing BETY:	  a symbol, growing b BETY, c symbol;
		  terminal BETY.

terminal b BETY:  b symbol, terminal BETY.

terminal b:	  b symbol.

a symbol:   "a".
b symbol:   "b".
c symbol:   "c".