替换

extern crate regex;
use regex::Regex;

fn main() {
    let rg = Regex::new(r"(\d+)").unwrap();

    // Regex::replace replaces first match 
    // from it's first argument with the second argument
    // => Some string with numbers (not really)
    rg.replace("Some string with numbers 123", "(not really)");

    // Capture groups can be accesed via $number
    // => Some string with numbers (which are 123)
    rg.replace("Some string with numbers 123", "(which are $1)");

    let rg = Regex::new(r"(?P<num>\d+)").unwrap();
    
    // Named capture groups can be accesed via $name
    // => Some string with numbers (which are 123)
    rg.replace("Some string with numbers 123", "(which are $num)");

    // Regex::replace_all replaces all the matches, not only the first
    // => Some string with numbers (not really) (not really)
    rg.replace_all("Some string with numbers 123 321", "(not really)");
}