Developer(s) Mathias Doenitz Written in Java | Development status Active Operating system | |
Initial release November 12, 2009; 7 years ago (2009-11-12) Stable release 1.1.7 / 9 February 2015; 2 years ago (2015-02-09) | ||
parboiled is an open-source Java library released under an Apache License. It provides support for defining PEG parsers directly in Java source code.
parboiled is commonly used as an alternative for regular expressions or parser generators (like ANTLR or JavaCC), especially for smaller and medium-size applications.
Apart from providing the constructs for grammar definition parboiled implements a complete recursive descent parser with support for abstract syntax tree construction, parse error reporting and parse error recovery.
Example
Since parsing with parboiled does not require a separate lexing phase and there is no special syntax to learn for grammar definition parboiled makes it comparatively easy to build custom parsers quickly.
Consider this the following classic “calculator” example, with these rules in a simple pseudo notation
Expression ← Term ((‘+’ / ‘-’) Term)* Term ← Factor (('*' / '/') Factor)* Factor ← Number / '(' Expression ')' Number ← [0-9]+With parboiled this rule description can be translated directly into the following Java code:
The class defines the parser rules for the language (yet without any actions), which could be used to parse actual input with code such as this: