how do I use look-around?

[zhguokai]

let regex = regex::Regex::new(r"(?<=#{)[^{}]+(?=})").unwrap();
let rule = "select ${abc} from #{b}";

for item in regex.captures_iter(rule) {
println!("{}", item.get(0).unwrap().as_str())
}

report:

called Result::unwrap() on an Err value: Syntax(

regex parse error:
    (?<=\${)[^{}]+(?=})
    ^^^^
error: look-around, including look-ahead and look-behind, is not supported

)

why

[zhguokai]

how to fix

[BurntSushi]

The first sentences of the docs for this crate address and explain why:

This crate provides a library for parsing, compiling, and executing regular expressions. Its syntax is similar to Perl-style regular expressions, but lacks a few features like look around and backreferences. In exchange, all searches execute in linear time with respect to the size of the regular expression and search text.

[zhguokai]

thanks, but how to fix it? change express like Perl ? or not support

[BurntSushi]

I think the docs are pretty clear. The feature you want isn't supported by this crate. You either need to stop using look-around, or use a different regex engine.

[zhguokai]

thanks, it is difficult for me to under the doc write in English, which regex engine can I use for look-around?

[zhguokai]

i will try "fancy-regex" ?

[BurntSushi]

Sure, go ahead. That's not my area of expertise.

[zhguokai]

fancy_regex