[aya eltokhy]

I wrote the following Prolog code for depth first search:

Code: Select all

domains
 
        sl=symbol*
predicates
        nondeterm parent(symbol,symbol)
        nondeterm getChildren(symbol,sl,sl)
        nondeterm member(symbol,sl)
        nondeterm add(sl,sl,sl,sl)
        nondeterm dfs(sl,sl,symbol)
clauses
        parent(a,b).
        parent(a,c).
        parent(a,d).
        parent(b,e).
        parent(b,f).
        parent(c,f).
        parent(c,g).
        parent(e,h).
        parent(e,i).
        parent(f,j).
        
        
        dfs(OPEN,CLOSE,END):-
                        OPEN=[],!,fail
                        ;
                        OPEN=[X|_],X=END,!,true
                        ;
                        getChildren(X,[],ChL),CLOSE2=[X|CLOSE],add(ChL,OPEN,CLOSE2,OPENF),
                        dfs(OPENF,CLOSE2,END).
        
        getChildren(X1,ChL,ChLF):-
                parent(X1,Ch),not(member(Ch,ChL)),!,ChL2=[Ch|ChL],
                getChildren(X1,ChL2,ChLF)
                ;
                ChLF=ChL.
                
                
        member(X,[X|_]).
        member(X,[_|T]):-
                member(X,T).
                
                
        add([],OPEN,_,OPENF):-OPENF=OPEN,!.
        add(ChL,OPEN,CLOSE,OPENF):-
                ChL=[H|T],not(member(H,OPEN)),not(member(H,CLOSE)),!,
                OPEN2=[H|OPEN],add(T,OPEN2,CLOSE,OPENF)
                ;
                ChL=[_|T],add(T,OPEN,CLOSE,OPENF).
        
 
goal
        %getChildren(a,[],CHLF).
        dfs([a],[],b).

However, I get the following error:

the variable is not bounded in this clause X

[George]

#1 : it is not the latest prolog version
#2 : try to avoid if -else statement for old prolog version..
#3 : instead, use backtracking - this will avoid this kind of issue..
#4 : for any personal support, send a email to : Georgeananth.prolog@gmail