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

 File: leftrec.pl

 Patrick Blackburn, 1999.
 Kristina Striegnitz, 2002.

 This file contains the specification of a context free
 grammar generating the language a^+b^+\{}. The grammar
 contains a left-recursive rule.

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

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

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

lex(a,x).
lex(b,y).

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