Parsing

Parsing is a fundamental task in many applications, from configuration files to domain-specific languages (although, configuration files are better parsed with a deserialization library such as serde).

Rust has several popular parsing libraries, each with different approaches and strengths. This section covers the most popular parsing libraries in the Rust ecosystem.

In general, if you want to parse binary data, the nom crate seems to be the most popular. For parsing text, both Chomsky and Pest are popular. But the choice of parsing library really boils down to the question of how you want to write your grammar: do you prefer a declarative approach or a procedural one?

nom

nom is a parser combinator library that enables you to build parsers by combining smaller parsing functions. It focuses on performance and low memory usage, making it ideal for binary formats, network protocols, and other performance-critical parsing tasks. nom uses macros and functions to create composable parsers and is particularly well-suited for byte-level parsing where you need fine-grained control over the parsing process.

Chumsky

Chumsky is a parser combinator library designed with ergonomics and error recovery in mind. It offers a friendly, declarative API that makes it easy to build complex parsers. Chumsky excels at parsing programming languages and other text formats where good error messages are important. It features strong typing, excellent error reporting, and the ability to create parsers that can recover from errors and continue parsing.

Pest

Pest is a parsing library for Rust that consumes a PEG grammar and generates a parser, complete with error reporting and recovery. Unlike nom and Chumsky, which build parsers through code, Pest uses separate grammar files with a specialized syntax similar to other PEG (Parsing Expression Grammar) tools.

lalrpop

LALRPOP is a parser generator that turns grammar files into Rust code. It uses LR(1) parsing techniques, making it powerful for parsing context-free grammars like programming languages. LALRPOP is particularly well-suited for creating parsers for statically-defined languages where you need precise control over grammar precedence and associativity. It integrates well with the Rust build system through a build script, automatically regenerating parser code when your grammar changes.

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