repeg is a java library to for creating parsers based on the principals of Parsing Expression Grammars (PEG).
This project was created back in 2010 but was cleaned up and published in 2019. Since it has only just been made public, consider this project in beta phase.
Work is ongoing to get this library published to maven central. First full release ETA end Q1-2020
- Java 1.8 or higher.
- Parsers/Expressions are defined in code (java) using fluent API. Ease of use and understanding are primary objectives of this project.
- Zero transitive dependencies -
repegdoes not require and further libraries - Plain old java (i.e. no byte code magic) so easy to integrate in restricted environments.
- Ability to define parsers in a dedicated DSL
- Generate standalone parser with no dependencies to
repeg - Built-in support for indented languages (such as python or yaml)
- Investigate ratpack style parsing (Tests so far do not suggest much need for this. I would welcome any feedback and examples of languages where ratpack parsing may be of an advantage).
This project comes with several examples which you can use to get you started:
- Calculator - parse and evaluate simple maths expressions such as
(7+2)*5. - Template - a very simple template language mimicking the style of jtwig.
- Todo - a parser for a text based todo list.
- IsoDuration - a (partial) implementation of a parser for ISO durations such as
P1Y6MT7M3S. - Persons (CSV) - an parser for CSV file containing person information.
- Persons (JSON) - same as above, but parsing JSON input.
Note: The last 3 examples are provided to show what can be done but not necessarily what should be done with repeg. A
parser for an ISO Duration can be hand-made relatively easily and will deliver much better performance. For common formats such
as CSV and JSON, there are plenty of specialised parsers/libraries available which will handle corner-cases better than the
examples and perform much better at the same time.