Parser Combinators

Simple implementation of a monadic parser in Java

Motivation

• Parsing things in Java is hard compared with functional languages that supports monadic parsers. This is a simple try to do these stuff in java.

• Introduce a tool to allow parsing recursive structures like JSON in an easy way

Prerequisites

Basic understanding of how parser combinators works, like how to "And" two parser.

Examples

example 1

import edu.parsec.data.list.IList;
import edu.parsec.parser.imp.Parser;
import edu.parsec.parser.combinators.Combinator;
import edu.parsec.parser.combinators.ParserBuilder;

public class IntegerParser {
	public Parser<Integer> integerParser() {
		Parser<Character> digitParser = ParserBuilder.anyCharOf("0123456789");
		Parser<IList<Character>> digits = Combinators.many1(digitParser);
		return digits.map(x -> x.foldLeft("", (acc, c) -> acc + String.valueOf(c))).map(Integer::parseInt);
	}
}

example 2

import edu.parsec.examples.json.data.JStr;
import edu.parsec.parser.combinators.ParserBuilder;
import edu.parsec.parser.combinators.Combinator;

public Parser<JStr> JStrParser() {
	Parser<Character> quote = ParserBuilder.parseChar('\"');
	Parser<String> str = Combinators.stringParser();
	return quote.then(str).skip(quote).map(JStr::new);
}

Challenges

• Making a better monadic interface. Right now the Monad interface is not type aware of the Monad class extending it. so I used bridge methods to narrow the types to make it suitable for the parser class.
• Make the parse faster by optimizing the building process.

License

This project is licensed under the MIT License - see the [LICENCE] file for details