带枚举的MiniZinc global_cardinality函数

Question

根据医生们

枚举类型的一个关键行为是，当它们被用于期望整数的位置时，它们会自动被强制到整数。例如，这允许我们使用在整数(如global_cardinality_low_up )上定义的全局约束。

global_cardinality*家族有两种类型:谓词和函数。在谓词的情况下，枚举项的数组确实会强迫ints，而强制的函数似乎不起作用。例如,

include "global_cardinality_closed.mzn";

enum MyEnum = {A, B, C};
array[1..2] of MyEnum: toCount = [A, C];

array[1..100] of var MyEnum: values;

%1
constraint let {
    array[int] of var int: counts = global_cardinality_closed(values, toCount);
} in counts[1] > counts[2];

%2
constraint global_cardinality_closed(values, toCount, [5, 6]);

在MiniZincIDE中编译上面的代码片段将得到以下结果：

MiniZinc: type error: no function or predicate with this signature found: `global_cardinality_closed(array[int] of var MyEnum,array[int] of MyEnum)'
Cannot use the following functions or predicates with the same identifier:
predicate global_cardinality_closed(array[$_] of var int: x,array[$_] of int: cover,array[$_] of var int: counts);
    (requires 3 arguments, but 2 given)

同时，%2之后的代码也编译得很好。

我是错过了什么，还是应该提交一个bug？

Answer 1

要使%1工作，您可以

include "global_cardinality_closed_fn.mzn";

或者简单的

include "globals.mzn";

函数是通过使用谓词实现的：

include "global_cardinality_closed.mzn";

/** @group globals.counting
  Returns an array with number of occurrences of \a cover[\p i] in \a x.

  The elements of \a x must take their values from \a cover.
*/
function array[$Y] of var int: global_cardinality_closed(array[$X] of var int: x,
                                                         array[$Y] of int: cover) :: promise_total =
  let { array[int] of int: cover1d = array1d(cover);
        array[index_set(cover1d)] of var 0..length(x): counts;
        constraint global_cardinality_closed(array1d(x),cover1d,counts); } 
  in arrayXd(cover,counts);