/****************************************************************

 File: epsilon.pl

 Kristina Striegnitz, 2002.

 This file contains the specification of a context free
 grammar generating the language a^*b^*\{}. The grammar
 contains an epsilon production. 

 You need a parser/recognizer that declares the following 
 operator:

 :- op(700,xfx,--->).
****************************************************************/

s ---> [].
s ---> [left,s,right].

lex(a,left).
lex(b,left).

/**********************************************************************
                    That's all, folks!
***********************************************************************/