搜索所有路径和一个图的最短路径 - 序言(search all paths and the shor

我在与涡轮Prolog的一个问题，搜索2个节点之间的图表中的所有路径和最短路径。我的问题是，以测试如果节点是在列表与否（构件的子句精确地）

           1    ---- b ----   3
           ---       |        ---
        ---          |             -----
      a              |5                  d
        ---          |             -----
            ---      |         ---
             2  ---  |     ---   4
                  -- c  --

for example we have for b--->c 
([b,c],5) , ([b,a,c],3) and ([b,d,c],7) : possible paths.
([b,a,c],3) : the shortest path.

这是我的代码：

DOMAINS
    list=Symbol *

PREDICATES
    distance(Symbol, Symbol)
    path1(Symbol, Symbol, list, integer)
    path(Symbol, Symbol,list, list, integer)
    distance(Symbol, list, integer)
    member(Symbol, list)
    shortest(Symbol, Symbol, list, integer)

CLAUSES
    distance(a, b, 1).
    distance(a, c, 2).
    distance(b, d, 3).
    distance(c, d, 4).
    distance(b, c, 5).
    distance(b, a, 1).
    distance(c, a, 2).
    distance(d, b, 3).
    distance(d, c, 4).
    distance(c, b, 5).

    member(X, [X|T]).
    member(X, [Y|T]) :- member(X, T).

    absent(X, L) :-
        member(X, L),
        !,
        fail.
    absent(_, _).

    /* find all paths */
    path1(X, Y, L, C) :- path(X, Y, L, I, C).
    path(X, X, [X], I, C) :- absent(X, I).
    path(X, Y, [X|R], I, C) :-
        distance(X, Z, A),
        absent(Z, I),
        path(Z, Y, R, [X|I], C1),
        C = C1 + A
        .

    /* to find the shortest path */
    shortest(X, Y, L, C) :-
        path(X, Y, L, C),
        path(X, Y, L1, C1),
        C < C1.

Answer 1:

这显示了最短路径，它的重量：

edge(a,b,6).
edge(a,c,1).
edge(b,d,5).
edge(c,e,4).
edge(c,f,1).
edge(d,h,3).
edge(e,h,7).
edge(f,g,2).
edge(g,h,1).

path(X,Y,M,[Y]) :- edge(X,Y,M).
path(X,Y,P,[Z|T]) :- edge(X,Z,M),path(Z,Y,N,T),
            P is M+N.

pravilo(X,Y,Z) :-  assert(min(100)),assert(minpath([])),!,
                path(X,Y,K,PATH1),
                (min(Z),K<Z,
                retract(min(Z));assert(min(K))),
                minpath(Q),retract(minpath(Q)),
                assert(minpath([X|PATH1])),
                fail.

?- pravilo(a,h,X);
    write("Minimal Path:"),
    minpath(PATH),
    write(PATH),
    nl,
    write("Path weight:"),
    min(Z),
    write(Z).