Поиск в весовом графе

domains
slist=string*
way=w(integer,slist)
ways=way*
 
predicates
nondeterm m(string,string,integer)
nondeterm move(string,string,integer)
nondeterm prolong(way,way)
place(ways,ways,ways)
placeone(way,ways,ways)
nondeterm search_bst(string,string)
nondeterm bst(ways,string,way)
nondeterm member(string,slist)
show_answer(slist)
 
clauses
m("a","b",10).
m("b","c",7).
m("a","d",3).
m("b","d",5).
m("c","d",15).
m("c","e",7).
m("d","e",5).
 
move(A,B,C):-m(A,B,C);m(B,A,C).
 member(H,[H|_]).
member(H,[_|Tail]):-member(H,Tail).
 
 prolong(w(Length,[Temp|Tail]),w(NewLength,[New,Temp|Tail])):-
    move(Temp,New,C),not(member(New,[Temp|Tail])),NewLength=Length+C.
 place([],SortedWays,SortedWays).
place([Way|Tail],PrevWays,SortedWays):-
    placeone(Way,PrevWays,PrevWays1),
    place(Tail,PrevWays1,SortedWays).
    
 placeone(w(Length,Way),[w(LengthH,WayH)|Tail],[w(Length,Way),w(LengthH,WayH)|Tail]):-Length<=LengthH,!.
placeone(LengthWay,[LengthHWayH|Tail],[LengthHWayH|NewTail]):-placeone(LengthWay,Tail,NewTail).
placeone(LengthWay,[],[LengthWay]).
 
 search_bst(Start,Finish):-
    bst([w(0,[Start])],Finish,w(Length,Way)),
    show_answer(Way),nl,write("Length of way: "),write(Length).
    
 bst([w(Length,[Finish|Tail])|_],Finish,w(Length,[Finish|Tail])).
bst([TempWay|OtherWays],Finish,Way):-
    findall(W,prolong(TempWay,W),Ways),
    place(Ways,OtherWays,NewWays),bst(NewWays,Finish,Way).
    
 show_answer([_]):-!.
show_answer([A,B|Tail]):-
    show_answer([B|Tail]),nl,write(B),write(" -> "),write(A).
 
goal
search_bst("aa","cc"),nl,nl,nl,fail.