Parse multiple inputs and discard everything non matching

Question

I have some input, let's say:

gibberishMATCHgibberishMATCHothergibberishMATCH

I have a parser for MATCH which works but I need a way to combine this so that I can parse a big string like above with inputs that can be anything and gives me a vector that contains every result of MATCH.

What's the way to do this?

Answer 1

I am not exactly sure what you are trying to do, since you did not provide an expected output, but the following would be my take on it:

use nom::{
    bytes::complete::tag,
    character::complete::anychar,
    multi::{many0, many_till},
    Finish, IResult, Parser,
};

fn main() {
    let input = "gibberishMATCHgibberishMATCHothergibberishMATCH";
    let result = parse(input).finish().unwrap().1;
    println!("{:#?}", result);
}

fn parse(input: &str) -> IResult<&str, Vec<&str>> {
    many0(many_till(anychar, parse_match).map(|r| r.1))(input)
}

fn parse_match(input: &str) -> IResult<&str, &str> {
    // Alternatively use is_a("xy")(input) or whatever you like.
    tag("MATCH")(input)
}

which would produce the following output:

[
    "MATCH",
    "MATCH",
    "MATCH",
]

Here is the corresponding Rust Playground link.

Explanation

The basic idea is to use many_till which yields a Vec of tuples, where the first value in the tuple is everything that matches anychar, until parse_match yields a result and the second value in the tuple is the result of parse_match.
Since we are not interested in the first value of the tuple, it is discarded using .map(|r| r.1).
Finally this process is continued using many0 until all matches in the input string are found.