pest 0.2.2

pest is a PEG parser generator with simplicity and speed in mind.

Documentation

Elegant

pest uses PEG syntax to enable expressive grammar creation.

impl_rdp! {
    grammar! {
      expression = _{ paren ~ expression? }
      paren      =  { ["("] ~ expression? ~ [")"] }
    }
}

let mut parser = Rdp::new(StringInput::new("(()((())())()")));

assert!(parser.expression());
assert!(parser.end());

Fast

pest generates a fast parser at compile time through the use of macros, without forcing you to use nightly. Yes, it works on stable (1.9.0+).

Tests have been run on an Intel Q8200, 4GB DDR2, Linux 4.6.2 as follows:

• ANTLR 4 [JSON grammar] (https://github.com/antlr/grammars-v4/blob/master/json/JSON.g4) measured with JMH SingleShotTime
• Bison + Flex JSON grammar with string capturing and printing removed
• pest JSON grammar measured with cargo bench

Features

• simple PEG grammar
• smart error reporting with atomic and silent rules
• precedence climbing rule
• no generation step (one-step compilation)
• fast macro-generated recursive descent parser
• runs on stable Rust
• elegant functional-style Token processing

Comparison

Short comparison with other parsing tools. Please take into consideration that pest is the youngest among them, but is continuously improving.

Roadmap

• Packrat parsing
• parsing parallelization