nom-recursive 0.5.1

Extension of nom to handle left recursion
Documentation 
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use nom::branch::*;
use nom::character::complete::*;
use nom::IResult;
use nom_locate::LocatedSpan;
use nom_recursive::{recursive_parser, RecursiveInfo};

type Span<'a> = LocatedSpan<&'a str, RecursiveInfo>;

pub fn expr(s: Span) -> IResult<Span, String> {
    alt((expr_binary, term))(s)
}

#[recursive_parser]
pub fn expr_binary(s: Span) -> IResult<Span, String> {
    let (s, x) = expr(s)?;
    let (s, y) = char('+')(s)?;
    let (s, z) = expr(s)?;
    let ret = format!("{}{}{}", x, y, z);
    Ok((s, ret))
}

pub fn term(s: Span) -> IResult<Span, String> {
    let (s, x) = char('1')(s)?;
    Ok((s, x.to_string()))
}

#[test]
fn test() {
    let ret = expr(LocatedSpan::new_extra("1", RecursiveInfo::new()));
    assert_eq!("\"1\"", format!("{:?}", ret.unwrap().1));

    let ret = expr(LocatedSpan::new_extra("1+1", RecursiveInfo::new()));
    assert_eq!("\"1+1\"", format!("{:?}", ret.unwrap().1));

    let ret = expr(LocatedSpan::new_extra(
        "1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1",
        RecursiveInfo::new(),
    ));
    assert_eq!(
        "\"1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1\"",
        format!("{:?}", ret.unwrap().1)
    );
}