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    star
    642
  • Rank 67,266 (Top 2 %)
  • Language
    Scala
  • License
    Apache License 2.0
  • Created over 10 years ago
  • Updated 21 days ago

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Repository Details

simple combinator-based parsing for Scala. formerly part of the Scala standard library, now a separate community-maintained module

scala-parser-combinators

This was originally part of the Scala standard library, but is now community-maintained, under the guidance of the Scala team at Lightbend. If you are interested in joining the maintainers team, please contact @Philippus or @SethTisue.

Choosing a parsing library

This library's main strengths are:

  • Stability. It's been around and in wide use for more than a decade.
  • The codebase is modest in size and its internals are fairly simple.
  • It's plain vanilla Scala. No macros, code generation, or other magic is involved.
  • Multiple versions of Scala (2.12, 2.13, 3) are supported on all back ends (JVM, JS, Native).

Its main weaknesses are:

  • Performance. If you are ingesting large amounts of data, you may want something faster.
  • Minimal feature set.
  • Inflexible, unstructured error reporting.

A number of other parsing libraries for Scala are available -- see list on Scaladex.

Documentation

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" % <version>

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

Scala.js and Scala Native

Scala-parser-combinators is also available for Scala.js and Scala Native:

libraryDependencies += "org.scala-lang.modules" %%% "scala-parser-combinators" % <version>

Example

import scala.util.parsing.combinator._

case class WordFreq(word: String, count: Int) {
  override def toString = s"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(s"FAILURE: $msg")
      case Error(msg,_) => println(s"ERROR: $msg")
    }
  }
}

For a detailed unpacking of this example see Getting Started.

Contributing

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