prolog：将列表的元素限制在一定范围内


Prolog: Constraining the elements of a list to be within a range

是否有任何方法可以将列表的元素限制在一个范围内(看起来更像是1-6，而不是使用between(1, 6, X)？

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相关讨论

clpfd库具有一个ins/2谓词，您可以在其中为变量列表指定元素的范围。

赞：

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all_between(Low, High, Vars) :-
    Vars ins Low..High.

调用all_between(1,6,[X1,X2,X3]).时，我们得到：

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X1 in 1..6,
X2 in 1..6,
X3 in 1..6.

如果要枚举元素，也可以使用label(L).来分配值：

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all_between_enumerate(Low, High, Vars) :-
    Vars ins Low..High,
    label(Vars).

对于all_between_enumerate(1,2,[X1,X2,X3]).，这将生成：

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?- all_between_enumerate(1,2,[X1,X2,X3]).
X1 = X2, X2 = X3, X3 = 1 ;
X1 = X2, X2 = 1,
X3 = 2 ;
X1 = X3, X3 = 1,
X2 = 2 ;
X1 = 1,
X2 = X3, X3 = 2 ;
X1 = 2,
X2 = X3, X3 = 1 ;
X1 = X3, X3 = 2,
X2 = 1 ;
X1 = X2, X2 = 2,
X3 = 1 ;
X1 = X2, X2 = X3, X3 = 2.

如果您已经将约束添加到变量中，例如X1 #< X3，则这些约束也要考虑在内：

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?- X1 #< X3, all_between_enumerate(1,2,[X1,X2,X3]).
X1 = X2, X2 = 1,
X3 = 2 ;
X1 = 1,
X3 = X2, X2 = 2.

您可以使用库CLPFD：

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:- use_module(library(clpfd)).

constraint_list([]).
constraint_list([H|T]):-H in 1..6 ,label([H]),constraint_list(T).

示例：

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?- constraint_list([X1,X2]).
X1 = X2, X2 = 2 ;
X1 = 2,
X2 = 3 ;
X1 = 2,
X2 = 4 ;
X1 = 2,
X2 = 5 ;
X1 = 3,
X2 = 2 ;
X1 = X2, X2 = 3 ;
X1 = 3,
X2 = 4 ;
X1 = 3,
X2 = 5 ;
X1 = 4,
X2 = 2 ;
X1 = 4,
X2 = 3 ;
X1 = X2, X2 = 4 ;
X1 = 4,
X2 = 5 ;
X1 = 5,
X2 = 2 ;
X1 = 5,
X2 = 3 ;
X1 = 5,
X2 = 4 ;
X1 = X2, X2 = 5.

?- L=[1,2,3] ,constraint_list(L).
false.

?- L=[2,2,3] ,constraint_list(L).
L = [2, 2, 3].

?- constraint_list(L).
L = [] ;
L = [2] ;
L = [2, 2] ;
L = [2, 2, 2] ;
L = [2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2|...] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2|...] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2|...] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2|...] ;
L = [2, 2, 2, 2, 2, 2, 2, 2, 2|...] .
    ... (and goes on)