lark-rust 0.1.1

High-performance Rust-accelerated drop-in replacement for lark's LALR parser stack

lark-rust

High-performance Rust-accelerated drop-in replacement for lark's LALR parser stack. A faster alternative to lark-cython.

Installation

pip install lark-rust

Usage

from lark import Lark
import lark_rust

parser = Lark(grammar, parser='lalr', _plugins=lark_rust.plugins)
result = parser.parse(text)

That's it — same lark API, just faster.

What's accelerated

The Rust native extension accelerates the hot-path components:

• Token — creation, hashing, equality comparison
• Scanner — regex matching via fancy-regex
• BasicLexer — token loop with single-pass newline counting
• LineCounter — position tracking
• LexerState — lexer state management

The parser, tree builder, and tree traversal are implemented in Python with full lark compatibility:

• ContextualLexer, LALR_Parser (with serialize/deserialize/on_error)
• ParseTreeBuilder with ExpandSingleChild, PropagatePositions, ChildFilter
• Tree with iter_subtrees, find_data, scan_values, pretty printing

lark-cython compatibility

lark-rust is a drop-in replacement for lark-cython. All plugins supported by lark-cython are supported:

• BasicLexer, ContextualLexer, LexerThread
• LALR_Parser, _Parser, ParseTreeBuilder

Requirements

• Python >= 3.8
• lark >= 1.0

License

MIT