prolog - 如何使用clpfd :automaton to restrict counter value in SICStus Prolog?

Question

我想实现一个非常简单的自动机，它限制 1 和 0 列表中连续 1 的数量(例如 [0,1,1,0,1,1,1])。

我的自动机看起来像这样:

% 'Day' is a list of clpfd variables
% 'Allowed' is an integer
%
% consecutiveOnes(+Day, +Allowed)
consecutiveOnes(Day, Allowed) :-

    automaton(Day, _, Day,
        [source(n)],
        [
         arc(n, 0, n, [0]  ),
         arc(n, 1, n, [C+1])
        ],
        [C],
        [0],
        [_N]
    ).



% example 1:
%   consecutiveOnes([0,0,0,1,1,1], 2)  -> there are three consecutive 1s and we allow only 2 -> Fail.

% example 2:
%   consecutiveOnes([0,1,1,1,0,0], 2)  -> there are three consecutive 1s and we allow only 2 -> Fail.


% example 3:
%   consecutiveOnes([0,1,1,0,0,0], 2)  -> there are only two consecutive 1s and we allow 2 -> OK

如何为计数器 C 添加约束指定 C <= Allowed到上面的 Prolog 代码？

Answer 1

最好用附加状态来表述它。例如，对于最多两个连续的 1:

:- use_module(library(clpfd)).

at_most_two_consecutive_ones(Day) :-
    automaton(Day,
        [source(n),sink(n),sink(n1),sink(n2)],
        [arc(n, 0, n),
         arc(n, 1, n1),
         arc(n1, 1, n2),
         arc(n1, 0, n),
         arc(n2, 1, false),
         arc(n2, 0, n)
        ]).

示例查询:

?- at_most_two_consecutive_ones([0,0,0,1,1,1]).
false.

?- at_most_two_consecutive_ones([0,1,1,0,1,1]).
true.

?- at_most_two_consecutive_ones([0,1,1,0,1,0]).
true.

对于更通用的解决方案，您必须在给定最大运行长度时按需构建自动机。