Prolog路径发现

Question

如果我有以下谓词门,声明两个房间之间有一扇门:

door(office, hall).
door(kitchen, office).
door(hall, "dining room").
door(kitchen, cellar).
door("dining room", kitchen).

并且谓词门户宣布门的状态:

doorstate(hall, office, closed).
doorstate(hall, "dining room", opened).
doorstate("dining room", kitchen, opened).
doorstate(kitchen, office, opened).
doorstate(kitchen, cellar, opened).

如果两个房间之间的所有门都打开,那么两个房间之间就有一条通道.

如何编写规则来发现两个房间之间是否存在这样的路径？

Answer 1

prolog的可怕恐怖回归太快了.

wayopen(Room1,Room2) :- doorstate(Room1, Room2, opened).
wayopen(Room1,Room2) :- doorstate(Room1, RoomX, opened), wayopen(RoomX,Room2).

所以我不只是为你做功课,这里是如何理解它:

• 两个房间之间的通道是开放的,如果它们是由一个门连接而且门打开了.
• 如果第一条路通向另一个房间的门,并且从另一个房间到第二个房间有一条路,那么两个房间之间的路是开放的.

请注意,这些规则只能在一个方向上通过门.你的功课是让它在两个方向都有效.

我们在哪里可以从大厅到达？

?- wayopen(hall, X).
X = diningroom ;
X = kitchen ;
X = office ;
X = cellar ;
false.

以下是您可以从中获取的所有房间:

?- wayopen(Room1,Room2).
Room1 = hall,
Room2 = diningroom ;
Room1 = diningroom,
Room2 = kitchen ;
Room1 = kitchen,
Room2 = office ;
Room1 = kitchen,
Room2 = cellar ;
Room1 = hall,
Room2 = kitchen ;
Room1 = hall,
Room2 = office ;
Room1 = hall,
Room2 = cellar ;
Room1 = diningroom,
Room2 = office ;
Room1 = diningroom,
Room2 = cellar ;
false.