Question

I got this code to return a shortest path between 2 cities:

goal(Z,Path,Cost) :-
    A = mycity,
    caminhAux2(A,[Z],0,Path, Cost).

caminhAux2(A,[A|Path1],Cost1,[A|Path1],Cost1).
caminhAux2(A,[Y|Path1],Cost1,Path,Cost) :-
    conn(_,X,Y,Dist,N),
    road(N,Vmed,_), 
    CostXY is Dist/Vmed,
    Cost2 is Cost1 + CostXY,
    caminhAux2(A,[X,Y|Path1],Cost2,Path,Cost).

best(Z,P,C) :-
    goal(Z,P,C),
    \+ (goal(Z,P1,C1),C1<C).

How I can make this to avoid already visited locations? This is in infinity cycling.

Answer 1

Easy: In the recursive clause of the strangely named “caminhAux2” predicate, it seems that X must not be a member of Path1, so at a place that I leave as an exercise, the goal \+ member(X, Path1) might do it?