combine
A Rust parser combinator library inspired by Haskell's Parsec, enabling modular LL(1) parsing with arbitrary lookahead.
What is combine?
Combine is a parser combinator library for Rust that enables developers to build parsers by combining smaller, reusable parsing functions. It solves the problem of writing complex parsers by providing high-level abstractions that reduce boilerplate and improve maintainability. Inspired by Haskell's Parsec, it supports LL(1) parsing with optional lookahead and handles various input streams efficiently.
Rust developers working on parsing tasks such as implementing domain-specific languages, parsing file formats, or building compilers and interpreters. It's particularly useful for those who prefer a modular, functional approach to parsing.
Developers choose Combine for its modular design, zero-copy parsing capabilities, and support for partial parsing, which makes it efficient and flexible. Its compatibility with arbitrary streams and inspiration from established libraries like Parsec provide a robust foundation for parsing in Rust.
Overview
A parser combinator library for Rust
Use Cases
Best For
- Building parsers for custom file formats or data serialization
- Implementing domain-specific languages (DSLs) in Rust
- Creating lexers and parsers for programming languages
- Parsing streaming data from network sockets or I/O devices
- Developing compiler frontends or interpreter components
- Writing efficient, zero-copy parsers for in-memory data structures
Not Ideal For
- Projects requiring extensive context-free or LR parsing, as Combine's default LL(1) approach may need cumbersome workarounds for complex grammars.
- Teams prioritizing immediate, out-of-the-box parsers for common formats like JSON or XML, where specialized libraries offer more convenience and less setup.
- Developers unfamiliar with functional programming concepts, as the combinator-based design can be less intuitive than imperative parsing methods.
Pros & Cons
Pros
Can parse from various sources including bytes, strings, iterators, and custom streams, as highlighted in the features section, making it adaptable to different data inputs without modification.
Specialized parsers in the range module allow parsing in-memory data without copying, optimizing performance for large datasets and reducing memory overhead.
Parsers can be stopped and resumed, ideal for handling streaming data from I/O devices like network sockets, as demonstrated in the async example and partial parsing documentation.
High-level combinators like many and sep_by enable building complex parsers from simple ones, reducing boilerplate and improving code reuse, inspired by Haskell's Parsec.
Cons
Error positions are based on pointer comparisons, leading to inscrutable debug info unless extra steps like using the State wrapper or translate_position are taken, as admitted in the FAQ.
The functional, combinator-based approach requires understanding of parser combinators, which can be challenging for developers accustomed to imperative or regex-based parsing techniques.
Default LL(1) parsing may not efficiently handle grammars that require more lookahead, necessitating the use of attempt combinators which can impact performance and add complexity.
Frequently Asked Questions
Related Projects
tree-sitterAn incremental parsing system for programming tools
nomRust parser combinator framework
pestThe Elegant Parser
lalrpopLR(1) parser generator for Rust
Found a gem we're missing?
Open-Awesome is built by the community, for the community. Submit a project, suggest an awesome list, or help improve the catalog on GitHub.