NetLogo嵌套ask中设置调用breed变量失败问题求助

你遇到的问题是：在嵌套ask结构里，子海龟无法通过set ([b] of myself) 14修改父海龟（turtle 0）的变量，报错提示“This isn't something you can use "set" on.”。

错误原因 #

([b] of myself)返回的是父海龟变量b的当前数值，而非变量本身。set命令需要直接指定变量名，不能对一个数值进行赋值操作，因此会报错。

解决方案 #

直接让父海龟自身执行变量赋值操作即可，使用ask myself [set b 14]替代原来的错误写法。myself在嵌套ask中指向发起当前嵌套调用的父海龟（这里就是turtle 0），通过ask myself可以让父海龟主动修改自己的变量。

修改后的go过程代码如下：

to go
  ask turtle 0 
  [
    set a 2
    set b 3 
    show (word "(a, b) = (" a ", " b ")")
    ask other turtles 
    [
      show (word "(a, b) = (" a ", " b ")")
      set a a + 1
      set b b + 1
      show (word "(a, b) = (" a ", " b ")")
      ; 替换为正确的写法
      ask myself [set b 14]
    ]
  ]
  tick
end

结果验证 #

运行一次go过程后，所有子海龟都会触发父海龟（turtle 0）将b设为14。下次运行go时，turtle 0的初始b值就会是14，输出结果符合你的预期：

(turtle 0): "(a, b) = (2, 14)"
(turtle 3): "(a, b) = (1, 1)"
(turtle 3): "(a, b) = (2, 2)"
(turtle 1): "(a, b) = (1, 1)"
(turtle 1): "(a, b) = (2, 2)"
(turtle 2): "(a, b) = (1, 1)"
(turtle 2): "(a, b) = (2, 2)"

内容的提问来源于stack exchange，提问作者mijen67