如何修复 NetLogo 6.0.4 中的“Nothing named ? has been defined”错误

Question

我下载了修改后的随机集群代码，用于使用 NetLogo 建模共享中修改后的随机集群方法的 Millington 版本生成中性景观模型。当我单击“generate-landscape”按钮时，代码中的“fill-landscape”过程会导致“Nothing named ? has been defined”错误。

当我创建附加的界面图像并尝试运行下面的相邻代码时。该问题似乎与“发生次数”报告功能中的问号有关。reduce 函数未按预期工作。有解决办法吗？查看界面，然后代码如下：

  ifelse ( any? neighbours with [ cluster != nobody ] )  ;; check if there are any assigned patches in neighbourhood
  [

    let covers []

    ask neighbours with [ cluster != nobody ]
    [
      set covers fput cover covers    ;;ask neighbours to add their covers to the list
    ]

    let unique-covers remove-duplicates covers    ;;create a list of unique covers

    let max-cover-count -1                 ;the number of neighbours with the maximum cover
    let max-cover -1                       ;the maximum cover

    ifelse(length unique-covers > 1)
    [
      ;if there is more than one unique-cover
      foreach unique-covers                  ;for each of the unique covers
      [
        let occ occurrences ? covers          ;count how many neighbours had this cover

        ifelse(occ > max-cover-count)        ;if the count is greater than the current maximum count
        [ 
          set max-cover ?                    ;set this as the dominant cover
          set max-cover-count occ            ;update the current maximum count

;---------------

to-report occurrences [x the-list]
  report reduce
    [ifelse-value (?2 = x) [?1 + 1] [?1]] (fput 0 the-list)
end 
;---------------    

该代码假设使用由 Saura 和 Martinez-Millan (2000) 开发的修改后的随机聚类方法生成中性景观模型。但是，错误“Nothing named ? has been defined”使代码无法顺利运行。期待思考……

Answer 1

?NetLogo 5.x 中的旧语法被->NetLogo 6 中的新语法替换。请参阅https://ccl.northwestern.edu/netlogo/docs/programming.html#anonymous-procedures

因此，例如，在 NetLogo 5 中，您将编写：

foreach [0 1 2 3] [
  print ?
]

在 NetLogo 6 中，你写：

foreach [0 1 2 3] [ x ->
  print x
]

Answer 2

Bryan 的答案（第一个过程）和 NetLogo 词典（第二个过程）的组合为您提供以下内容。注释指出了新的位。未测试。

ifelse ( any? neighbours with [ cluster != nobody ] )
[ let covers []
  ask neighbours with [ cluster != nobody ]
  [ set covers fput cover covers
  ]
  let unique-covers remove-duplicates covers
  let max-cover-count - 1  ; added a space around subtraction
  let max-cover - 1        ; more spacing
  ifelse(length unique-covers > 1)
  [ foreach unique-covers
    [ this-cover ->                  ; here's the new bit, calling ? 'this-cover'
      let occ occurrences this-cover covers ; passes to the occurrences procedure
      ifelse(occ > max-cover-count)
      [ set max-cover this-cover     ; using the name this-cover again
        set max-cover-count occ

reduce对于出现的情况，您可以直接从 NetLogo Dictionary示例中获取过程

to-report occurrences [#x #the-list]
  report reduce
    [ [occurrence-count next-item] -> ifelse-value (next-item = #x)
        [occurrence-count + 1] [occurrence-count] ] (fput 0 #the-list)
end