prolog

edge(1,5).
edge(2,1).
edge(3,1).
edge(4,3).
edge(5,8).
edge(6,4).
egde(7,5).
edge(8,6).
edge(1,7).
egde(2,7).
edge(3,6).
edge(4,5).
egde(6,5).
edge(8,5).

%?-path(1,6,[1],path).

path(Node,Node,_,[Node]).

path(Start,Finissh,Visited,[Start|Path]):-edge(start,X), not(member(X , Visited)),

                                         path(X,Finish,[Start|visited], path).

% depth first search in direct graph

path(Node,Node,_,[Node]).
path(Start,Finish,Visited,[Start|Path]):-edge(Start,X),
                                        %not(members(X,Visited),
                                         members(X,Visited),
                                         Path(X,Finish,[X|Visited],Path).

members(_,[]).
members(X,[H|T):- \+X=H,members(X,T).