| # Features | |
| ## Main Features | |
| - Earley parser, capable of parsing any context-free grammar | |
| - Implements SPPF, for efficient parsing and storing of ambiguous grammars. | |
| - LALR(1) parser, limited in power of expression, but very efficient in space and performance (O(n)). | |
| - Implements a parse-aware lexer that provides a better power of expression than traditional LALR implementations (such as ply). | |
| - EBNF-inspired grammar, with extra features (See: [Grammar Reference](grammar.md)) | |
| - Builds a parse-tree (AST) automagically based on the grammar | |
| - Stand-alone parser generator - create a small independent parser to embed in your project. | |
| - Flexible error handling by using a "puppet parser" mechanism (LALR only) | |
| - Automatic line & column tracking (for both tokens and matched rules) | |
| - Automatic terminal collision resolution | |
| - Standard library of terminals (strings, numbers, names, etc.) | |
| - Unicode fully supported | |
| - Extensive test suite | |
| - MyPy support using type stubs | |
| - Python 2 & Python 3 compatible | |
| - Pure-Python implementation | |
| [Read more about the parsers](parsers.md) | |
| ## Extra features | |
| - Import rules and tokens from other Lark grammars, for code reuse and modularity. | |
| - Support for external regex module ([see here](classes.md#using-unicode-character-classes-with-regex)) | |
| - Import grammars from Nearley.js ([read more](nearley.md)) | |
| - CYK parser | |
| - Visualize your parse trees as dot or png files ([see_example](https://github.com/lark-parser/lark/blob/master/examples/fruitflies.py)) | |
| ### Experimental features | |
| - Automatic reconstruction of input from parse-tree (see examples) | |
| ### Planned features (not implemented yet) | |
| - Generate code in other languages than Python | |
| - Grammar composition | |
| - LALR(k) parser | |
| - Full regexp-collision support using NFAs | |