Sample code of "Creating DSL With Antlr4 and Scala" for Scala2.13

Arithmetic.scala

import java.io.ByteArrayInputStream

import org.antlr.v4.runtime.{CharStream, CharStreams, CommonTokenStream}

/**
 * See original Saumitra's blog.
 * https://saumitra.me/blog/creating-dsl-with-antlr4-and-scala/
 *
 * This code is for Scala 2.13.
 */
object Arithmetic {
  def main(args: Array[String]): Unit = {
    expressions.foreach(parse)
  }

  def parse(input:String) = {
    println ("\nEvaluating expression " + input)

    val charStream = CharStreams.fromStream(new ByteArrayInputStream(input.getBytes("utf-8")))
    val lexer = new ArithmeticLexer(charStream)
    val tokens = new CommonTokenStream(lexer)
    val parser = new ArithmeticParser(tokens)

    val arithmeticListener = new ArithmeticListenerApp()

    parser.expr.enterRule(arithmeticListener)
  }

  val expressions = List(
    "127.1 + 2717",
    "2674 - 4735",
    "47 * 74.1",
    "271 / 281",
    "12 ^ 3"               // unsupported expression
  )
}