NetLogo 5.1.0转6.3.0：A*算法代码兼容问题求助

核心问题原因 #

NetLogo 6.x 对匿名函数语法做了重大调整，旧版本（5.x）中使用?1、?2指代参数的写法已被弃用，sort-by要求传入接收两个参数的二元箭头函数，用于判断元素的排序规则。

正确的排序代码替换 #

将原代码中的错误排序行：

; set open sort-by [[f] of ?1 < [f] of ?2] open
set open sort-by < [] open

替换为以下两种兼容写法之一：

写法1（显式变量访问，更直观）：

set open sort-by [ [a b] -> [f] of a < [f] of b ] open

写法2（NetLogo 6.x 简化语法，更简洁）：

set open sort-by [ [a b] -> a.f < b.f ] open

修正后的完整A*路径查找代码 #

to-report find-a-path [ source-patch destination-patch]

  ; initialize all variables to default values
  let search-done? false
  let search-path []
  let current-patch 0
  set open []
  set closed []

  ; add source patch in the open list
  set open lput source-patch open

  ; loop until we reach the destination or the open list becomes empty
  while [ not search-done? ]
  [
    ifelse length open != 0
    [
      ; sort the patches in open list in increasing order of their f() values
      ; 替换为NetLogo 6.x兼容的排序写法
      set open sort-by [ [a b] -> a.f < b.f ] open

      ; take the first patch in the open list
      ; as the current patch (which is currently being explored (n))
      ; and remove it from the open list
      set current-patch item 0 open
      set open remove-item 0 open

      ; add the current patch to the closed list
      set closed lput current-patch closed

      ; explore the Von Neumann (left, right, top and bottom) neighbors of the current patch
      ask current-patch
      [
        ; if any of the neighbors is the destination stop the search process
        ifelse any? neighbors4 with [ pxcor = [pxcor] of destination-patch and pycor = [pycor] of destination-patch ]
        [
          set search-done? true
        ]
        [
          ; the neighbors should not be obstacles or already explored patches (part of the closed list)
          ask neighbors4 with [ pcolor != black and not member? self closed and self != parent-patch ]
          [
            ; the neighbors to be explored should also not be the source or
            ; destination patches or already a part of the open list (unexplored patches list)
            if not member? self open and self != source-patch and self != destination-patch
            [
              ;set pcolor 45

              ; add the eligible patch to the open list
              set open lput self open

              ; update the path finding variables of the eligible patch
              set parent-patch current-patch
              set g [g] of parent-patch + 1
              set h distance destination-patch
              set f (g + h)
            ]
          ]
        ]
      ]
    ]
    ; 补充原代码缺失的else分支（处理open列表为空的情况）
    [
      set search-done? true
      ; 可选：添加路径查找失败的提示
      ; print "No path found!"
    ]
  ]
  ; 补充原代码缺失的report语句（回溯生成路径）
  if search-done? and current-patch != 0 [
    set search-path lput current-patch search-path
    while [ [parent-patch] of last search-path != source-patch ] [
      set search-path lput [parent-patch] of last search-path search-path
    ]
    set search-path lput source-patch search-path
  ]
  report search-path
end

额外注意事项 #

1. 必须在代码开头定义patch的私有变量，否则会报错：

patches-own [
  parent-patch
  g
  h
  f
]

2. 原代码缺失while循环的else分支和最终的report语句，修正代码中已补充，保证逻辑完整性。

内容的提问来源于stack exchange，提问作者Mats Hiemink