Geek Answers Handbook

Regular expression matching string starting with offset

I am learning Rust and trying to write a simple tokenizer right now. I want to go through the line that executes each regular expression against the current position in the line, create a token, then skip ahead and repeat until I process the entire line. I know that I can put them in a larger regular expression and cyclically capture them, but I need to process them separately for domain resons.

However, I do not see anywhere in the regex box that allows offset, so I can start matching again at a specific point.

extern crate regex;
use regex::Regex;

fn main() {

    let input = "3 + foo/4";

    let ident_re = Regex::new("[a-zA-Z][a-zA-Z0-9]*").unwrap();
    let number_re = Regex::new("[1-9][0-9]*").unwrap();
    let ops_re = Regex::new(r"[+-*/]").unwrap();
    let ws_re = Regex::new(r"[ \t\n\r]*").unwrap();

    let mut i: usize = 0;

    while i < input.len() {

        // Here check each regex to see if a match starting at input[i]
        // if so copy the match and increment i by length of match.
    }
}

, , . , ( ), .

+4
1

. - , . , , , , .

fn main() {
    let mut s = "hello";
    while !s.is_empty() {
        println!("{}", s);
        s = &s[1..];
    }
}

, , utf8- char -. O (1) O (n), , , , utf8.

+6

More articles:


All Articles