Lexing和解析CSS层次结构 [英] Lexing and Parsing CSS hierarchy

问题描述

.someDiv { width:100%; height:100%; ... more properties ... }

我如何在解析器中构成一个与上面的字符串匹配的规则?

How would I make up a rule in my parser that will match the string above?

对我来说似乎不太可能，因为您不能在规则中定义无限数量的属性?有人可以澄清一下，您将如何使用FsLex和FsYacc做这样的事情?

Seems rather impossible for me, since you cant define an unlimited amount of properties in the rule? Could someone please clarify, how you would do such a thing with FsLex and FsYacc?

推荐答案

如果您使用的是FsLex和FsYacc，则可以将{ ... }内部的属性解析为属性列表.假设您有一个能够正确识别所有特殊字符的词法分析器，并且具有解析单个属性的规则，则可以编写如下内容:

If you're using FsLex and FsYacc then you can parse the properties inside { ... } as a list of properties. Assuming you have a lexer that properly recognizes all the special characters and you have a rule that parses individual property, you can write something like:

declaration:
  | navigators LCURLY propertyList RCURLY { Declaration($1, $3) }
  | navigators LCURLY RCURLY              { Declaration($1, []) }

propertyList:
  | property SEMICOLON propertyList    { $1::$2 }
  | property                           { [$1] }

property:
  | IDENTIFIER COLON values            { Property($1, $3) }

declaration规则解析整个声明(您需要为可以在CSS中使用的各种导航器(例如div.foo #id等)编写解析器.)propertyList规则解析一个属性，然后递归调用自身解析多个属性.

The declaration rule parses the entire declaration (you'll need to write parser for various navigators that can be used in CSS such as div.foo #id etc.) The propertyList rule parses one property and then calls itself recursively to parse multiple properties.

在右侧构造的值将是代表各个属性的值的列表. property规则解析单个属性分配，例如width:100%(但是您需要完成值的解析，因为它可以是列表或更复杂的表达式).

The values constructed on the right-hand-side are going to be a list of values representing individual property. The property rule parses individual property assignment e.g. width:100% (but you'll need to finish parsing of values, because that can be a list or a more compelx expression).

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