序言中的错误 "illegal variable type for this position "

Question

我试着搜索动物，谁有这个属性，但是我有一个错误"illegal variable type for this position "。如何解决？

domains
type=symbol
object=symbol
property=symbol
value=symbol
parent=symbol
predicates
nondeterm is_a(type, parent) 
nondeterm has_prop(object, property, value) 
nondeterm has_property(object, property, value) 
clauses
is_a(dog,wolf).
is_a(dingo,wolf).
is_a(wolf,volki).
is_a(coyote,volki).
is_a(jackal,volki).
is_a(volki,dogs).
is_a(fox,dogs).
is_a(arctic_fox,dogs).

has_prop(dogs, travel, walk). 
has_prop(dogs, food_for_child, milk).  
has_prop(volki, size, medium). 
has_prop(volki, color, brown). 
has_prop(arctic_fox, color, white). 
has_prop(arctic_fox, size, small). 
has_prop(fox, color, orange). 
has_prop(fox, size, small). 
has_prop(wolf, color, grey). 
has_prop(wolf, size, large). 
has_prop(dog, color, brown). 
has_prop(dog, size, small). 
has_prop(dingo, color, orange). 
has_prop(dingo, size, medium). 



has_property(Object, Property, Value):-
has_prop(Object, Property, Value). 
has_property(Object, Property, Value):-
is_a(Object,Parent), 
has_property(Parent, Property, Value).

goal
has_property(X,size,medium).

我在这一行有一个错误 "illegal variable type for this position ":

is_a(Object,Parent),

Answer 1

抱歉，我没有可用于测试的 Visual Prolog，所以我不太确定解决方案，但我认为问题在于您应该明确 domains 和 predicates 元素是 ground 项。所以我建议要么让它们小写，要么用连字符括起来，否则它们是 variables:

domains
 type=symbol
 object=symbol
...

predicates
 is_a(type, parent) 
...

或

domains
 'Type'=symbol
 'Object'=symbol
...

predicates
 is_a('Type', 'Parent') 
...

编辑

如果您有可用的 SWI-Prolog，只需注释掉文件开头到 domains 包含的内容。或者在 SWISH 上查看 this notebook。

Answer 2

问题出在类型和变量上。我删除域并使用简单类型。

正确的代码：

predicates
nondeterm is_a(symbol, symbol) 
nondeterm has_prop(symbol, symbol, symbol) 
nondeterm has_property(symbol, symbol, symbol) 
clauses
is_a(dog,wolf).
is_a(dingo,wolf).
is_a(wolf,volki).
is_a(coyote,volki).
is_a(jackal,volki).
is_a(volki,dogs).
is_a(fox,dogs).
is_a(arctic_fox,dogs).

has_prop(dogs, travel, walk). 
has_prop(dogs, food_for_child, milk).  
has_prop(volki, size, medium). 
has_prop(volki, color, brown). 
has_prop(arctic_fox, color, white). 
has_prop(arctic_fox, size, small). 
has_prop(fox, color, orange). 
has_prop(fox, size, small). 
has_prop(wolf, color, grey). 
has_prop(wolf, size, large). 
has_prop(dog, color, brown). 
has_prop(dog, size, small). 
has_prop(dingo, color, orange). 
has_prop(dingo, size, medium). 


has_property(O, Property, Value):-
has_prop(O, Property, Value). 
has_property(O, Property, Value):-
is_a(O,Parent), 
has_property(Parent, Property, Value).

goal
has_property(X,size,medium).

序言中的错误 "illegal variable type for this position "

Error "illegal variable type for this position " in prolog

visual-prolog