Opal

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.