parser-lang
_{^{PARSER INFRASTRUCTURE}}

parser-lang is the MAIN-tier crate that follows: Recursive-descent + combinator infra with error recovery and Pratt/precedence. HQL unblocks here. Part of the -lang language-construction family; see _strategy/LANG_COLLECTION.md for the master plan.

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MSRV is 1.85+ (Rust 2024 edition).

Status: stable. The public API is frozen as of 1.0.0 and follows Semantic Versioning — no breaking changes before 2.0. See CHANGELOG.md.

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Installation

[dependencies]
parser-lang = "1"

Example

A calculator that evaluates 1 + 2 * 3 to 7 with correct precedence — a Pratt grammar over a token-lang stream.

use parser_lang::{Parser, Pratt, Span, Token, TokenKind};

#[derive(Clone, Copy)]
enum K { Num(i64), Plus, Star, Eof }
impl TokenKind for K {
    fn is_eof(&self) -> bool { matches!(self, K::Eof) }
}

struct Calc;
impl<'t> Pratt<'t, K> for Calc {
    type Output = i64;
    fn prefix(&mut self, p: &mut Parser<'t, K>) -> Option<i64> {
        match p.bump()?.kind() { K::Num(n) => Some(*n), _ => None }
    }
    fn infix_binding(&self, k: &K) -> Option<(u8, u8)> {
        match k { K::Plus => Some((1, 2)), K::Star => Some((3, 4)), _ => None }
    }
    fn infix(&mut self, op: &'t Token<K>, l: i64, r: i64) -> Option<i64> {
        match op.kind() { K::Plus => Some(l + r), K::Star => Some(l * r), _ => None }
    }
}

let s = |i| Span::new(i, i + 1);
let tokens = [
    Token::new(K::Num(1), s(0)), Token::new(K::Plus, s(1)),
    Token::new(K::Num(2), s(2)), Token::new(K::Star, s(3)),
    Token::new(K::Num(3), s(4)), Token::new(K::Eof, Span::empty(5)),
];
let mut p = Parser::new(&tokens);
assert_eq!(Calc.parse(&mut p), Some(7));

Status

This is v1.0.0: the public API is stable and frozen under SemVer. The Parser cursor (with error recovery) and the Pratt precedence engine are complete and catalogued in docs/API.md.

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Contributing

See dev/DIRECTIVES.md for engineering standards and the definition of done. Before a PR: cargo fmt --all, cargo clippy --all-targets --all-features -- -D warnings, and cargo test --all-features must be clean.

License

Licensed under either of

• Apache License, Version 2.0 — LICENSE-APACHE
• MIT License — LICENSE-MIT

at your option.

^{COPYRIGHT © 2026 James Gober .}