jrudolph / fastparsers

Fast Parser Combinators

FastParsers

FastParsers is a Scala parser library which uses macros to transform easy-to-write parser combinators into efficient recursive-descent backtracking parsers. The generated parsers are about 20x faster than Scala's parser combinator library even though its interface stay about the same.

Here is an example of a basic JSON parser

val jsonParser = FastParser {
 def value: Parser[Any] = obj | arr | stringLit |
                          decimalNumber | "null" | "true" | "false"
 def obj: Parser[Any] = lit("{") ~> repsep (member, ",") <~ "}"
 def arr: Parser[Any] = lit("[") ~> repsep (value , ",") <~ "]"
 def member: Parser[Any] = stringLit ~ (lit(":") ~> value)
}

This generate a Parser Object which allow you to call any of the transformed rules.

val cnt = "{\"firstName \": \"John\" , \"age\": 25}"
jsonParser.value (cnt) match {
      case Success ( result ) =>
        println ("success : " + result )
      case Failure ( error ) =>
        println (" failure : " + error )
}

For a more comprehensive presentation please take a look at the presentation slides.

To have a better understanding of the internals please read the paper describing the implementation.