algorithm - Minizinc错误：无效的类型输入：预期为“ float”，实际为“ var float”

我有以下Minizinc程序，正在逐步解决旅行商问题（TSP）。我知道它不仅会解决此错误，而且我仍然想了解为什么会收到此错误。下面的可复制示例：

include "globals.mzn";

% Input Parameters 
int: NUM_POINTS;
float: MAX_TOTAL_DISTANCE;
array[0..NUM_POINTS-1] of int: points;
array[0..NUM_POINTS-1, 0..NUM_POINTS-1] of float: distance_matrix;

% Decision Variable: where to go next, from each point (indexed on points)
array[0..NUM_POINTS-1] of var 0..NUM_POINTS-1: next_point;  

% Constraints that define a valid tour
constraint alldifferent(next_point);  % each point only visited once
constraint next_point[NUM_POINTS-1] == points[0];  % not sure if this is helpful or not?

% see if we can find a feasible solution below max-total-distance
float: total_distance = sum(p in points)(distance_matrix[points[p],next_point[p]]);
constraint total_distance < MAX_TOTAL_DISTANCE;
solve satisfy;

output[show(total_distance) ++ "\n" ++ show(next_point)];

我得到的错误是：

MiniZinc：类型错误：“ total_distance”的初始化值具有无效的类型输入：预期的“ float”，实际的“ var float”

我猜这是因为next_point在的计算中使用total_distance，并且next_point它是决策变量（var），这意味着也total_distance需要吗？但是，如果更改float: total_distance...为，则会var float: total_distance...在其他地方出现新错误：

MiniZinc：类型错误：'points'的初始化值具有无效的type-in​​st：预期的'int的array [int]，实际的'float的array [int，int]'

我能否仅不基于函数（例如，求和），参数和决策变量来定义变量？我想我这里缺少基本的东西。（以下示例数据为可复制示例）：

% DATA (in my setup this is in a dzn file)
NUM_POINTS = 5;
points = [|
0, 0|
0, 0.5|
0, 1|
1, 1|
1, 0|];
distance_matrix = [|
0.0, 0.5, 1.0, 1.41, 1.0 |
0.5, 0.0, 0.5, 1.12, 1.12 |
1.0, 0.5, 0.0, 1.0, 1.41 |
1.41, 1.12, 1.0, 0.0, 1.0 |
1.0, 1.12, 1.41, 1.0, 0.0 |];