The Parsing Expression Grammar Template Library (PEGTL) is a C++11 library for creating parsers according to a Parsing Expression Grammar (PEG). Grammars are written as regular C++ code, created with template programming (not template meta programming), i.e. nested template instantiations that naturally correspond to the inductive definition of PEGs.
A comprehensive set of parser rules that can be combined and extended by the user is included, as are mechanisms for debugging grammars and attaching user-defined actions to grammar rules. Here is an example of how a PEG grammar rule is implemented as C++ class with the PEGTL.
// PEG rule for integers consisting of a non-empty
// sequence of digits with an optional sign:
// integer ::= ( '+' / '-' )? digit+
// The same parsing rule as PEGTL class:
struct integer
: pegtl::seq< pegtl::opt< pegtl::one< '+', '-' > >,
pegtl::plus< pegtl::digit > > {};PEGs are superficially similar to Context-Free Grammars (CFGs), however the more deterministic and procedural nature of PEGs gives rise to some very important differences. For an in-depth description see Wikipedia page on PEGs or this paper on PEGs by Bryan Ford.
The PEGTL was initially developed in 2008 as an experiment in C++0x based on ideas from the YARD library by Christopher Diggins. Several years of real-world experience and smaller updates passed until 2014, when some of the more experimental PEGTL features were removed, and the remaining parts refactored and refined.
For questions and suggestions please contact the authors at pegtl (at) colin-hirsch.net.
- Getting Started
- Calculator Example
- Rules and Grammars
- Actions and States
- Rule Reference
- Parser Reference
- Contrib Reference
- Control Hooks
- Advanced Rules
- Grammar Analysis
- 2014 Refactoring
A new changelog will start here soon.
Copyright (c) 2014-2015 Dr. Colin Hirsch and Daniel Frey
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