Crate nom_recursive

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Expand description

nom-recursive is an extension of nom to handle left recursion.


The following example show a quick example. If #[recursive_parser] is removed, stack overflow will occur because of infinite recursion.

use nom::branch::*;
use nom::character::complete::*;
use nom::IResult;
use nom_locate::LocatedSpan;
use nom_recursive::{recursive_parser, RecursiveInfo};

// Input type must implement trait HasRecursiveInfo
// nom_locate::LocatedSpan<T, RecursiveInfo> implements it.
type Span<'a> = LocatedSpan<&'a str, RecursiveInfo>;

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

// Apply recursive_parser by custom attribute
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()))

fn main() {
    let ret = expr(LocatedSpan::new_extra("1+1", RecursiveInfo::new()));
    println!("{:?}", ret.unwrap().1);




Attribute Macros