How do I parse expressions with operator precedence in jparsec?

Use the built-in operator precedence grammar functions like `Operators.expression()` to define rules declaratively, similar to BNF, which simplifies handling complex expressions. Refer to the wiki for detailed examples.

jparsec vs ANTLR for Java parsing?

jparsec offers a declarative, code-integrated approach with precise error reporting, ideal for DSLs, while ANTLR is better for complex grammars with generated code and extensive tooling. jparsec avoids external build steps, but ANTLR has broader ecosystem support.

How to handle errors accurately in jparsec parsers?

jparsec automatically tracks error locations with line and column numbers; you can customize messages using the `ParseError` class. The rich combinator set includes methods like `or()` for error recovery strategies.

Can jparsec parse large files efficiently?

Not natively; jparsec parses entire inputs in memory, so for large files, you may need custom streaming implementations. The README suggests alternatives like Google Mug Dot Parse for streaming support.

Is jparsec still maintained in 2025?

As of the 2025 update, the project recommends using Google Mug Dot Parse for Java 21+, indicating limited active development. Check the GitHub repository for recent commits or issues.

How to build a JSON parser with jparsec?

Start with basic parsers for tokens like strings and numbers using combinators like `Terminals.StringLiteral`, then combine them with `sequence()` and `many()` for structures. The wiki provides guides and examples for such implementations.

Open-Awesome

jparsec

Apache-2.0Javajparsec-root-3.1

A pure Java library for building recursive-descent parser combinators, inspired by Haskell Parsec.

GitHub

356 stars58 forks0 contributors

What is jparsec?

jparsec is a parser combinator library for Java that allows developers to build recursive-descent parsers using a functional, compositional approach. It solves the problem of parsing complex grammars by providing a declarative API that resembles BNF, along with accurate error location and operator precedence support.

Target Audience

Java developers who need to implement custom parsers for domain-specific languages, configuration files, or data formats without relying on external parser generators.

Value Proposition

Developers choose jparsec for its pure Java implementation, rich set of combinators, and the ability to define parsers declaratively, which reduces boilerplate and improves readability compared to traditional parsing approaches.

Overview

Build parsers in Java

Use Cases

Best For

Implementing parsers for domain-specific languages in Java
Parsing configuration files with custom syntax
Building expression evaluators with operator precedence
Creating data format parsers without external tools
Educational projects to learn parser combinator concepts
Prototyping grammars with quick iteration

Not Ideal For

Projects targeting Java 21+ that prioritize modern features like Stream integration and smaller library footprints
Applications requiring built-in lazy or streaming parsing out-of-the-box without custom implementation
Teams seeking pre-built parsers for common formats like CSV or regex, as jparsec requires building from scratch

Pros & Cons

Pros

Operator Precedence Grammar

Built-in support for defining operator precedence and associativity rules, enabling straightforward parsing of expressions without manual handling.

Accurate Error Location

Pinpoints parsing errors with precise line and column information, as highlighted in the README, which aids in debugging complex grammars.

Declarative BNF-like API

Allows grammar specification in a style resembling Backus-Naur Form, promoting readability and maintainability, as stated in the key features.

Rich Combinator Functions

Includes a comprehensive set of reusable parser combinators for common tasks, reducing boilerplate code, as noted in the documentation.

Cons

Risk of Infinite Loops

The API can lead to infinite loops or accidental left recursions with zero-consumption parsers, a known issue that's painful to debug, as admitted in the README's comparison to Google Mug Dot Parse.

No Native Streaming Support

Lacks built-in lazy or streaming parsing capabilities, requiring custom workarounds for large inputs, unlike modern alternatives mentioned in the news section.

Outdated for Modern Java

Does not fully embrace modern Java features like Stream or pattern matching, and has a larger footprint compared to newer libraries, as highlighted in the 2025 update.

Frequently Asked Questions

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