1
我正在处理的一个简单的Prolog程序的这部分应该找到距离给定点最远一定距离的坐标列表。我的代码工作,但也产生给定列表中的每个元素的错误。错误:类型错误:`file_path'预计
代码:
nearby_places(Places, Position, Signal, NearbyPlaces) :-
findall(
X,
(
Places,
member(X, Places),
is_reachable(Position, X, Signal)
),
NearbyPlaces
).
is_reachable(Position, Target, Signal) :-
manhattan_distance(Position, Target, Distance),
Distance =< Signal * 3.
manhattan_distance(pos(X1, Y1), pos(X2, Y2), Distance) :-
Dx is X1 - X2,
Dy is Y1 - Y2,
ADx is abs(Dx),
ADy is abs(Dy),
Distance is ADx + ADy.
试运行:
?- nearby_places([pos(0,0), pos(1,1), pos(2, 50), pos(4, 9)], pos(0,0), 10, N).
ERROR: Type error: `file_path' expected, found `pos(0,0)'
ERROR: Type error: `file_path' expected, found `pos(1,1)'
ERROR: Type error: `file_path' expected, found `pos(2,50)'
ERROR: Type error: `file_path' expected, found `pos(4,9)'
N = [pos(0, 0), pos(1, 1), pos(4, 9)].
所有我做了测试,产生正确的结果,但也是这些错误。 我还没有发现任何东西,甚至远程有用的任何地方。 我在Linux上使用SWI-Prolog 5.10.4。
谢谢你的时间!