Parser Comparison

This page provides a comprehensive comparison of actual parser generators and parser combinator libraries covered in this guide. Each parser uses different parsing algorithms and techniques, making them suitable for different language implementation scenarios.

Legend

🟢 Full support
🟡 Partial support or with limitations
🔴 Not supported

Parser Overview

Parser	Type	Algorithm	Grammar Format	Performance	Error Recovery	Learning Curve	Production Ready	Best For
nom	Parser Combinator	Recursive Descent	Rust combinators	⭐⭐⭐⭐⭐	⭐⭐	⭐⭐⭐⭐	⭐⭐⭐⭐⭐	Binary formats, streaming protocols
pest	Parser Generator	PEG	External `.pest` files	⭐⭐⭐	⭐⭐⭐⭐	⭐⭐	⭐⭐⭐⭐	Prototyping, DSLs, configuration languages
lalrpop	Parser Generator	LALR(1)	External `.lalrpop` files	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐⭐⭐	Production compilers, programming languages
chumsky	Parser Combinator	Recursive Descent	Rust combinators	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐	⭐⭐⭐	Error recovery, IDE support
winnow	Parser Combinator	Recursive Descent	Rust combinators	⭐⭐⭐⭐⭐	⭐⭐	⭐⭐⭐	⭐⭐⭐⭐	Successor to nom, cleaner API
pom	Parser Combinator	Recursive Descent	Rust combinators	⭐⭐⭐⭐	⭐⭐	⭐⭐⭐	⭐⭐⭐	Simple parsers, educational

Parsing Algorithm Characteristics

Algorithm	Left Recursion	Ambiguity	Backtracking	Memory Usage	Parse Time	Lookahead
LALR(1)	🟢 Handles naturally	🔴 Must resolve	🔴 None	Low	O(n)	1 token
PEG	🔴 Requires rewriting	🟢 First match wins	🟢 Unlimited	Medium	O(n) typical, O(n²) worst	Unlimited
Recursive Descent	🔴 Stack overflow	🟢 Can handle	🟢 Manual	Low	O(n) to O(n²)	Unlimited

Detailed Feature Comparison

Feature	nom	pest	lalrpop	chumsky	winnow	pom
Grammar Definition
External grammar files	🔴	🟢	🟢	🔴	🔴	🔴
Inline in Rust code	🟢	🔴	🔴	🟢	🟢	🟢
Type-safe	🟢	🟡	🟢	🟢	🟢	🟢
Grammar validation	Runtime	Runtime	Compile-time	Runtime	Runtime	Runtime
Parsing Features
Streaming input	🟢	🔴	🔴	🟡	🟢	🔴
Zero-copy parsing	🟢	🟢	🟢	🟡	🟢	🟢
Incremental parsing	🔴	🔴	🔴	🔴	🔴	🔴
Memoization/Packrat	🔴	🟢	🔴	🟡	🔴	🟡
Custom lexer support	🟢	N/A	🟢	🟢	🟢	🟢
Error Handling
Error recovery	🔴	🟢	🟡	🟢	🔴	🔴
Custom error types	🟢	🟢	🟢	🟢	🟢	🟢
Error position tracking	🟢	🟢	🟢	🟢	🟢	🟢
Multiple errors	🔴	🟢	🔴	🟢	🔴	🔴
Contextual errors	🟢	🟢	🟡	🟢	🟢	🟡
AST Generation
Automatic AST generation	🔴	🟡	🟢	🔴	🔴	🔴
Custom AST types	🟢	🟢	🟢	🟢	🟢	🟢
Location spans	🟢	🟢	🟢	🟢	🟢	🟢
Development Experience
IDE support	🟡	🟡	🟡	🟡	🟡	🟡
Debugging tools	🟡	🟢	🟢	🟢	🟡	🟡
Documentation quality	⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐

Grammar Complexity Support

Feature	nom	pest	lalrpop	chumsky	winnow	pom
Grammar Types
Context-free	🟢	🟢	🟢	🟢	🟢	🟢
Context-sensitive	🟢	🔴	🔴	🟡	🟢	🟡
Ambiguous grammars	🟢	🟡	🔴	🟢	🟢	🟢
Advanced Features
Left recursion	🟡*	🔴	🟢	🔴	🟡*	🔴
Operator precedence	Manual	🟢	🟢	🟢	Manual	Manual
Parameterized rules	🟢	🔴	🟢	🟢	🟢	🟢
Semantic predicates	🟢	🟢	🔴	🟢	🟢	🟢

*Can be handled with special combinators or techniques

tl;dr Recommendations

Choose nom when:

Parsing binary formats or network protocols
Need streaming/incremental parsing
Performance is critical
Want fine-grained control over parsing

Choose pest when:

Rapid prototyping of new languages
Grammar readability is important
Need good error messages out of the box
Working with configuration languages or DSLs

Choose lalrpop when:

Building production programming language compilers
Grammar has left recursion
Need maximum parsing performance
Want compile-time grammar validation

Choose chumsky when:

Error recovery is critical (IDE/LSP scenarios)
Need excellent error messages
Building development tools
Want modern combinator API

Choose winnow when:

Starting a new project (nom successor)
Want cleaner API than nom
Need streaming support
Performance is important

Choose pom when:

Learning parser combinators
Building simple parsers
Want minimal dependencies
Prefer simple, readable code

In short:

For maximum performance: LALRPOP (with grammar restrictions) or nom/winnow (with flexibility)
For best developer experience: pest (external grammars) or chumsky (error recovery)
For binary formats: nom or winnow are specifically designed for this
For production compilers: LALRPOP provides the traditional compiler construction approach
For learning: pom offers the simplest mental model

Each parser makes different trade-offs between performance, expressiveness, error handling, and ease of use. Consider your specific requirements carefully when making a selection.

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