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是否可以覆盖 rebol 路径运算符？

发布于 2024-08-09 09:20:10 字数 67 浏览 3 评论 0原文

可以覆盖 rebol 系统单词，如 print、make 等，那么是否可以对路径运算符执行相同的操作？那么语法是什么呢？

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始于初秋 2024-08-16 09:20:10

另一种可能的方法是使用 REBOL 元编程功能并预处理您自己的代码以捕获路径访问并添加处理程序代码。这里有一个例子：

apply-my-rule: func [spec [block!] /local value][
    print [
        "-- path access --" newline
        "object:" mold spec/1 newline
        "member:" mold spec/2 newline
        "value:" mold set/any 'value get in get spec/1 spec/2 newline
        "--"
    ]
    :value
]

my-do: func [code [block!] /local rule pos][
    parse code rule: [
        any [
            pos: path! (
                pos: either object? get pos/1/1 [
                    change/part pos reduce ['apply-my-rule to-block pos/1] 1
                ][
                    next pos
                ]
            ) :pos
            | into rule    ;-- dive into nested blocks
            | skip         ;-- skip every other values
        ]
    ]
    do code
]

;-- example usage -- 

obj: make object! [
    a: 5
]

my-do [
    print mold obj/a
]

这将为您提供：

-- path access --
object: obj
member: a
value: 5
--
5

另一种（较慢但更灵活）的方法也可以是将字符串模式的代码传递给预处理器，从而使您摆脱任何 REBOL 特定语法规则，如：然后，

my-alternative-do {
    print mold obj..a
}

预处理器代码将发现所有 .放置并更改代码以正确插入对“apply-my-rule”的调用，并最终使用以下命令运行代码：

do load code

在运行时可以处理和更改整个代码的程度没有真正的限制（所谓的）第一个示例的“块模式”是最有效的方式）。

Another possible approach is to use REBOL meta-programming capabilities and preprocess your own code to catch path accesses and add your handler code. Here's an example :

apply-my-rule: func [spec [block!] /local value][
    print [
        "-- path access --" newline
        "object:" mold spec/1 newline
        "member:" mold spec/2 newline
        "value:" mold set/any 'value get in get spec/1 spec/2 newline
        "--"
    ]
    :value
]

my-do: func [code [block!] /local rule pos][
    parse code rule: [
        any [
            pos: path! (
                pos: either object? get pos/1/1 [
                    change/part pos reduce ['apply-my-rule to-block pos/1] 1
                ][
                    next pos
                ]
            ) :pos
            | into rule    ;-- dive into nested blocks
            | skip         ;-- skip every other values
        ]
    ]
    do code
]

;-- example usage -- 

obj: make object! [
    a: 5
]

my-do [
    print mold obj/a
]

This will give you :

-- path access --
object: obj
member: a
value: 5
--
5

Another (slower but more flexible) approach could also be to pass your code in string mode to the preprocessor allowing freeing yourself from any REBOL specific syntax rule like in :

my-alternative-do {
    print mold obj..a
}

The preprocessor code would then spot all .. places and change the code to properly insert calls to 'apply-my-rule, and would in the end, run the code with :

do load code

There's no real limits on how far you can process and change your whole code at runtime (the so-called "block mode" of the first example being the most efficient way).

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