A zero-dependency C++ header-only parser combinator library for creating parsers according to Parsing Expression Grammars.
PEGTL is a C++ header-only library for creating parsers using Parsing Expression Grammars (PEGs). It enables developers to define grammars directly in C++ code through template programming, eliminating the need for external parser generators. The library provides a comprehensive set of parsing rules, grammar analysis tools, and mechanisms for attaching custom semantic actions.
C++ developers who need to implement parsers for custom file formats, domain-specific languages, or data processing tasks. It's particularly suited for those who prefer compile-time grammar definitions and want full control over parsing semantics.
Developers choose PEGTL for its zero-dependency, header-only design that simplifies integration, its ability to write grammars as native C++ code, and its emphasis on simplicity and efficiency. It offers more flexibility and control compared to traditional parser generators while maintaining high performance.
Parsing Expression Grammar Template Library
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As a zero-dependency header-only library, PEGTL can be seamlessly integrated into any C++ project without external build steps or dependencies, simplifying setup and deployment.
Grammars are written as regular C++ code using template instantiations, enabling compile-time checking and tight integration with the rest of the C++ ecosystem, as shown in the integer rule example.
The library includes a wide range of built-in parser rules, from basic character matching to complex combinators, reducing the need to implement common parsing patterns from scratch.
Users can attach custom actions to grammar rules, allowing for the construction of data structures or on-the-fly evaluation, demonstrated in examples like JSON parsing and arithmetic expression handling.
PEGTL's grammar analysis automatically detects PEG-specific issues such as left recursion, helping ensure the correctness and reliability of parsing logic during development.
Defining grammars requires advanced knowledge of C++ template syntax and patterns, which can be daunting for developers not versed in template metaprogramming, increasing the initial learning curve.
Since grammars are implemented using compile-time templates, complex parsers can lead to significantly longer compilation times, especially in large projects with extensive grammar definitions.
Unlike parser generators that auto-generate AST classes, PEGTL requires users to write all semantic actions from scratch, adding development overhead for building data structures or handling semantics.
The README explicitly warns that the main branch can undergo incompatible changes, forcing teams to rely on specific releases for stability, which may delay access to latest features or fixes.