英文:
Parse a string quoted by " in rust using lalrpop
问题
如何使用lalrpop在Rust中解析由双引号引用的字符串？
Str: Vec<u8> = {
"\"\"" <s:r"([^"])*"> "\"\"" => {
s.bytes().collect()
},
};
这并不起作用，我尝试在不同位置放置\，但由于文档中关于正则表达式的信息不多，我还没有弄清楚。
英文:
How to parse a string quoted by " in rust using lalrpop?
Str: Vec<u8> = {
"\"" <s:r"([^\"])*"> "\"" => {
s.bytes().collect()
},
};
This doesn't work and I tried putting \ at different places but haven't figured it out since there isn't much about regex in the docs.
答案1
得分: 2
Lalrpop的文档具体讨论了这个问题：
> 如果需要嵌入引号，可以使用哈希符号，例如 r#"..."..."#。
在Rust中，r"..." 是原始字符串，意味着所有非引号字符都被直接处理，包括 \。原始字符串没有转义字符，但当你在开头使用 r#" 而不是 r" 时，字符串不会结束，直到找到 "#。你可以使用任意数量的 # 字符来实现这一点，所以下面这些都是相同的字符串。
"hello"
r"hello"
r#"hello"#
r##"hello"##
r###"hello"###
以此类推。这允许你用足够多的周围 # 符号来转义任何数量的 "。
对于这个（以及大多数情况），这有点过于复杂了。对于你的正则表达式，你只需要一组周围的 #，如文档所示，它看起来是这样的。
r#"([^"])*"#
然而，如果你想要一个排除 " 和 # 的正则表达式，可以这样做：
r##"([^"#])*"##
请注意，这样做是因为正则表达式通常使用大量的 \，这会让转义变得麻烦。你也可以使用带有转义引号的普通字符串（至少在Rust中是这样，我没有尝试在lalrpop中使用）。
"([^\"])*"
英文:
Lalrpop's documentation talks about this specifically:
> you can use hashes if you need to embed quotes, like r#"..."..."#.
In rust, r"..." is a raw string, meaning all non-quote characters are taken literally, including \. There is no escape character for raw strings, but when you put r#" instead of r" at the beginning, the string won't end until it finds "#. You can do this with any number of # characters, so these are all the same string.
"hello"
r"hello"
r#"hello"#
r##"hello"##
r###"hello"###
And so on. This allows you to escape any " followed by any number of # with sufficient surrounding # symbols.
All that is a little overkill for this (and most things). For your regex, you just need one set of surrounding #, as the documentation shows, which looks like this.
r#"([^"])*"#
However, if you wanted a regex that excluded " and #, you could do:
r##"([^"#])*"##
Note that this is done because regexes often use lots of \, which would make escaping it annoying. You can also put a normal string with an escaped quote (at least in rust, I haven't tried it with lalrpop).
"([^\"])*"
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