Rebol / Red语言初始化

Question

在http://business-programming.com/business_programming.html#section-2.6上给出的示例：

REBOL []
items: copy []               ; WHY NOT JUST "items: []"
prices: copy []              ; WHY NOT JUST "prices: []"
append items "Screwdriver"
append prices "1.99"
append items "Hammer"
append prices "4.99"
append items "Wrench"
append prices "5.99"

为什么要做items: copy []而不是items: []？是否应该对所有变量初始化进行此操作，还是需要一些选择性类型？

编辑：我发现以下代码可以正常工作：

REBOL []
items: []   
prices: []  
append items "Screwdriver"
append prices "1.99"
append items "Hammer"
append prices "4.99"
append items "Wrench"
append prices "5.99"

probe items
probe prices

items: []   
prices: []  
append items "Screwdriver"
append prices "1.99"
append items "Hammer"
append prices "4.99"
append items "Wrench"
append prices "5.99"

probe items
probe prices

输出正常：

["Screwdriver" "Hammer" "Wrench"]
["1.99" "4.99" "5.99"]
["Screwdriver" "Hammer" "Wrench"]
["1.99" "4.99" "5.99"]

但不遵循：

REBOL []

myfn: func [][
    items: []   
    prices: []  
    append items "Screwdriver"
    append prices "1.99"
    append items "Hammer"
    append prices "4.99"
    append items "Wrench"
    append prices "5.99" ]

do myfn
probe items
probe prices

do myfn
probe items
probe prices

此处的输出重复：

["Screwdriver" "Hammer" "Wrench"]
["1.99" "4.99" "5.99"]
["Screwdriver" "Hammer" "Wrench" "Screwdriver" "Hammer" "Wrench"]
["1.99" "4.99" "5.99" "1.99" "4.99" "5.99"]

只有初始化在函数中时才会出现问题吗？

显然，默认情况下，函数中的所有变量都被视为全局变量，并且在启动时仅创建一次。似乎该语言正在将我的函数转换为：

items: []   
prices: []  
myfn: func [][
    append items "Screwdriver"
    append prices "1.99"
    append items "Hammer"
    append prices "4.99"
    append items "Wrench"
    append prices "5.99" ]

现在多次调用myfn的响应是可以理解的。 在循环中创建的全局函数也只创建一次。

Answer 1

此脚本中不需要copy []，因为当它再次运行时，系列items和prices的所有先前引用都将重新创建。

但如果items: []可能会在同一个脚本中运行多次，那么您需要复制以确保每次都创建一个新系列，而不仅仅是引用现有的系列。