如何高效优雅的解析类似下面的表达式 - V2EX
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my3157

如何高效优雅的解析类似下面的表达式

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  •   my3157 Aug 21, 2017 3112 views
    This topic created in 3170 days ago, the information mentioned may be changed or developed.

    优雅 + 高效

    其中, arch os id 为变量

    arch=x86 and ( os=linux or os=darwin ) or id>20 !(os=windows) 

    需要支持常见逻辑判断, 如下:

    = 相等 > 大于 >= 大于或等于 < 小余 <= 小余或等于 != 不等于 ! 取反 

    表达式从左到右解析, 遇到 () 先解析

    以上的基础上, 如何加入内置函数支持, 如下:

    len(os)=5 // 字符串 os 长度为 5 
    3 replies    2017-08-21 16:01:08 +08:00
    my3157
        1
    my3157  
    OP
       Aug 21, 2017
    有做过类似的功能的童鞋么? 给个思路
    Kilerd
        2
    Kilerd  
       Aug 21, 2017 via iPhone
    请复习编译原理等相关课程。

    文法不会很难啊
    my3157
        3
    my3157  
    OP
       Aug 21, 2017
    @Kilerd 初步想法是构建一个 tree, 从左到右解析, 数据结构大致如下:

    ```
    type Express struct {
    Left *Express
    Operation Operation
    Right *Express
    }
    ```
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