Parsing Expression Grammars in Rust

Documentation | Release Notes

pegtastic is an experimental third party fork of rust-peg. This fork is not ready for general consumption yet.

rust-peg is a simple yet flexible parser generator based on the Parsing Expression Grammar formalism. It provides a Rust macro that builds a recursive descent parser from a concise definition of the grammar.

Features

• Parse input from &str, &[u8], &[T] or custom types implementing traits
• Customizable reporting of parse errors
• Rules can accept arguments to create reusable rule templates
• Precedence climbing for prefix/postfix/infix expressions
• Helpful rustc error messages for errors in the grammar definition or the Rust code embedded within it
• Rule-level tracing to debug grammars

Example

pegtastic::parser!{
  grammar list_parser() for str {
    rule number() -> u32
      = n:$(['0'..='9']+) { n.parse().unwrap() }
    
    pub rule list() -> Vec<u32>
      = "[" l:number() ** "," "]" { l }
  }
}

pub fn main() {
    assert_eq!(list_parser::list("[1,1,2,3,5,8]"), Ok(vec![1, 1, 2, 3, 5, 8]));
}

See the tests for more examples
Grammar rule syntax reference in rustdoc

Comparison with similar parser generators