SComb: Simple but Powerful Parser Combinator Library in Scala

SComb (su-ko-n-bu) is a simple but powerful parser combinator library written in Scala. SComb aims to replace scala-parser-combinators.

Features of SComb (0.8.1):

• primitive combinators
  • string literal ( "" )
  • regular expression literal ( "".r )
  • any character (wildcard) ( any )
  • character set ( set(...) )
• rule combinator
  • used in right-hand side of non-teriminal
• the other combinators
  • zero or one ( e.? )
  • zero or more ( e.* )
  • one or more ( e.+ )
  • interleaving ( repead0By, repeat1By )
  • handling left-associativity ( chainl )
  • methods to use for-comprehension ( map , flatMap filter )
• the combinators for better error reporting
  • commit and withErrorMessage , to convert the failure to error parser

Install SComb

Add the following line to your build.sbt

libraryDependencies += "com.github.kmizu" %% "scomb" % "0.9.0"

Getting Started

You can write your own parser by inheriting com.github.kmizu.scomb.SCombinator[T] :

import com.github.kmizu.scomb.SCombinator

object IntegerParser extends SCombinator[Int] {
  override def root: P[Int] = rule {
    (digit.*).map{ case digits => digits.mkString.toInt }
  }
  lazy val digit: P[String] = set('0'to'9')
  
  def main(args: Array[String]): Unit = {
    assert(parse("100") == Success(100))
  }
}

In this example, P[Int] indicates that the parse result is Int . digit defined using set combinator matches one of character from [0-9]. digit.* matches the repetition of digit and the result is translated to Int by map{ case digits => digits.mkString.toInt } . Finally, a rule must be enclosed by rule { ... } combinator.

More Information

Some examples are below:

• CalculatorSpec
  • Arithmetic Expression Parser
• JsonSpec
  • JSON Parser
• RegularExpressionSpec
  • (Basic) Regular Expression Parser
• PrimitiveSpec
  • Tests of primitive combinators

Scaladoc

Here