%
% logic.pl -- the Knight/Knave identifier...
%
% Author:
%
% Comments:
%



% some "nice" prolog settings...  see assignment 8's
% description for the details on what these do
% -- but it's not crucial to know the details of these Prolog internals
:- set_prolog_flag( prompt_alternatives_on, groundness ).
:- set_prolog_flag(toplevel_print_options, [quoted(true),
     portray(true), attributes(portray), max_depth(999), priority(699)]).


%
% noVars( X ) is true if X is an expression that does not
%	      contain any logical variables, that is, no
%	      integers. (The expressions will not hold any
%	      Prolog variables in any case... .)
%
%	      Remember that you'll need one more rule here
%	      for expressions with only ONE subexpression!
%
noVars( t ).
noVars( f ).
noVars( [_, L, R] ) :- noVars( L ), noVars( R ).



%
% getVar( Expr, N ) is true if Expr is an expression with a
%	      logical variable, that is, an integer
%	      Then, N should be bound to one of those
%	      available variables (again, an integer)
%
%	      Remember that you'll need one more rule here
%	      for expressions with only ONE subexpression!
%
getVar( N, N ) :- number( N ).
getVar( [_, L, R], N ) :- getVar( L, N ); (noVars(L), getVar( R, N)).