带枚举的 MiniZinc global_cardinality 函数答案

【问题标题】：MiniZinc global_cardinality function with enums带枚举的 MiniZinc global_cardinality 函数
【发布时间】：2021-04-04 19:26:57
【问题描述】：

根据the docs

枚举类型的一个关键行为是，当它们用于需要整数的位置时，它们会自动强制转换为整数。例如，这允许我们使用定义在整数上的全局约束，例如 global_cardinality_low_up

global_cardinality* 系列有两种形式：谓词和函数。虽然在谓词的情况下，枚举项数组确实强制转换为整数，但强制似乎不起作用。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 sn-p 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之后的代码编译就好了。

我错过了什么还是应该提交错误？

【问题讨论】：

标签： minizinc

【解决方案1】：

要使%1 工作，您可以

include "global_cardinality_closed_fn.mzn";

或者干脆

include "globals.mzn";

该功能是利用谓词实现的：

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);

【讨论】：