/* File: gram2.pl
   Author: Mihaela Malita
   Title: Grammar for L(G)= a^n b^n 
  
	?-start.
        Grammar for a^n b^n
        Input a word: aabb.
        Generated
        Continue(y/n)?= y.
        Grammar for a^n b^n
        Input a word as a list: aab.
        Not generated
        Continue(y/n)?= n.

*/

	s --> [a],[b].
	s --> [a],s,[b].
  

  start:- write('Grammar for a^n b^n'),nl,
 	  write('Input a word: '),read(A),atom_chars(A,L),
	  (phrase(s,L) -> write('Generated') ; write('Not generated')),
          nl,yesorno,start.


  yesorno:- write('Continue(y/n)?= '),read(R),R=y.