A minimal, self-contained library of monadic parser combinators for OCaml, enabling easy construction of recursive-descent parsers.
Opal is a lightweight, monadic parser combinator library for OCaml that simplifies the creation of recursive-descent parsers. It provides a pure-functional, minimal set of essential parsers and combinators, enabling developers to build complex parsers by combining simpler ones. The library is designed to be self-contained, implemented in about 150 lines of OCaml, making it easy to embed directly into projects without heavy dependencies.
OCaml developers who need to write custom parsers, such as those implementing domain-specific languages, data format parsers, or solving parsing challenges like Hackerrank FP problems. It is particularly suited for those who prefer a minimal, functional approach without external dependencies.
Developers choose Opal for its minimalism and practicality, offering only the most essential tools in a single file, inspired by Haskell's Parsec but adapted for OCaml. Its small footprint and pure-functional design make it ideal for embedding directly into source code, reducing overhead compared to larger parsing libraries.
Self-contained monadic parser combinators for OCaml
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Implemented in about 150 lines of OCaml, it can be embedded directly into projects as a single file without external dependencies, reducing overhead.
Uses monadic operations like `>>=` and `<|>` to build parsers composably, inspired by Haskell's Parsec for a pure-functional approach that simplifies recursive-descent parsing.
Supports lazy streams for efficient parsing of large inputs, with built-in functions like `LazyStream.of_string` and `LazyStream.of_channel` for flexible input handling.
Provides derived combinators such as `many`, `choice`, `between`, and `chainl1` to handle typical parsing patterns, easing implementation of expression grammars and structured text.
Parsers return `None` on failure without any error details, making debugging difficult for complex grammars where pinpointing issues is crucial.
Requires developers to manually write parsers without grammar analysis, which can be error-prone for left-recursive rules and lacks the automation of parser generators.
Documentation is sparse and self-described as a 'rip-off of Parsec's doc,' lacking tutorials or extensive examples beyond basic arithmetic, which may hinder onboarding.