% word(X,Y,Z) is true if XYZ forms a 3-letter word.

word(a,d,d).
word(a,d,o).
word(a,g,e).
word(a,g,o).
word(a,i,d).
word(a,i,l).
word(a,i,m).
word(a,i,r).
word(a,n,d).
word(a,n,y).
word(a,p,e).
word(a,p,t).
word(a,r,c).
word(a,r,e).
word(a,r,k).
word(a,r,m).
word(a,r,t).
word(a,s,h).
word(a,s,k).
word(a,u,k).
word(a,w,e).
word(a,w,l).
word(a,y,e).
word(b,a,d).
word(b,a,g).
word(b,a,n).
word(b,a,t).
word(b,e,e).
word(b,o,a).
word(e,a,r).
word(e,e,l).
word(e,f,t).
word(f,a,r).
word(f,a,t).
word(f,i,t).
word(l,e,e).
word(o,a,f).
word(r,a,t).
word(t,a,r).
word(t,i,e).

% crosswd(P11,P12,P13,P21,P22,P23,P31,P32,P33) is true if these
% letters solve the crossword
crosswd(P11,P12,P13,P21,P22,P23,P31,P32,P33)<-
   word(P11,P12,P13) &
   word(P11,P21,P31) &
   word(P21,P22,P23) &
   word(P12,P22,P32) &
   word(P31,P32,P33) &
   word(P13,P23,P33).

% Example Query:
% ask crosswd(P11,P12,P13,P21,P22,P23,P31,P32,P33).