scala-parser-combinators

Scala Standard Parser Combinator Library

This library is now community-maintained. If you are interested in helping please contact @gourlaysama or mention it on Gitter.

As of Scala 2.11, this library is a separate jar that can be omitted from Scala projects that do not use Parser Combinators.

Documentation

Current API
The Getting Started guide
A more complicated example, Building a lexer and parser with Scala's Parser Combinators
"Combinator Parsing", chapter 33 of Programming in Scala, Third Edition, shows how to use this library to parse arithmetic expressions and JSON. The second half of the chapter examines how the library is implemented.

Adding an SBT dependency

To depend on scala-parser-combinators in SBT, add something like this to your build.sbt:

libraryDependencies += "org.scala-lang.modules" %% "scala-parser-combinators" % "1.1.0"

(Assuming you're using a scalaVersion for which a scala-parser-combinators is published. The first 2.11 milestone for which this is true is 2.11.0-M4.)

To support multiple Scala versions, see the example in scala/scala-module-dependency-sample.

Example

import scala.util.parsing.combinator._

case class WordFreq(word: String, count: Int) {
    override def toString = "Word <" + word + "> " +
                            "occurs with frequency " + count
}

class SimpleParser extends RegexParsers {
    def word: Parser[String]   = """[a-z]+""".r       ^^ { _.toString }
    def number: Parser[Int]    = """(0|[1-9]\d*)""".r ^^ { _.toInt }
    def freq: Parser[WordFreq] = word ~ number        ^^ { case wd ~ fr => WordFreq(wd,fr) }
}

object TestSimpleParser extends SimpleParser {
    def main(args: Array[String]) = {
        parse(freq, "johnny 121") match {
            case Success(matched,_) => println(matched)
            case Failure(msg,_) => println("FAILURE: " + msg)
            case Error(msg,_) => println("ERROR: " + msg)
        }
    }
}

For a detailed unpacking of this example see Getting Started.

ScalaJS support

Scala-parser-combinators directly supports scala-js 0.6+, starting with v1.0.5:

libraryDependencies += "org.scala-lang.modules" %%% "scala-parser-combinators" % "1.1.0"

Contributing

See the Scala Developer Guidelines for general contributing guidelines
Have a look at existing issues
Ask questions and discuss on Gitter