trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Expr
class Num(val value: Int) extends Expr
class Var(val name: String) extends Expr
class Mul(val left: Expr, val right: Expr) extends Expr

// Extractors here:
// apply is the injection
// unapply is the extraction

trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Expr
case class Num(val value: Int) extends Expr
case class Var(val name: String) extends Expr
case class Mul(val left: Expr, val right: Expr) extends Expr

object CaseClass extends App {
	val numObj = new Num(1)
	val varObj = new Var("var")

trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Expr
class Num(val value: Int) extends Expr
class Var(val name: String) extends Expr
class Mul(val left: Expr, val right: Expr) extends Expr

object Typecase extends App {
	val numObj = new Num(1)
	val varObj = new Var("var")

trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Expr
class Num(val value: Int) extends Expr
class Var(val name: String) extends Expr
class Mul(val left: Expr, val right: Expr) extends Expr

object TypeTestCast extends App {
	val numObj = new Num(1)
	val varObj = new Var("var")

trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Visitor[T] {
	def caseMul(t: Mul): T = otherwise(t)
	def caseNum(t: Num): T = otherwise(t)
	def caseVar(t: Var): T = otherwise(t)
	def otherwise(t: Expr): T = throw new NullPointerException
}

trait Expr {

trumanw

// Cited from the essay "Matching Object With Patterns"
// Class hierarchy:
trait Expr {
	def isVar: Boolean = false
	def isNum: Boolean = false
	def isMul: Boolean = false
	def value: Int = throw new NullPointerException
	def name: String = throw new NullPointerException
	def left: Expr = throw new NullPointerException
	def right: Expr = throw new NullPointerException

trumanw

import java.io._

// Pickling binary
import scala.pickling._
import binary._
import scala.pickling.Defaults._

// msgpack
import org.msgpack.annotation.Message
import org.msgpack.ScalaMessagePack

trumanw

import java.io._

@SerialVersionUID(124L)
class Person(var name: String)
extends Serializable {
    override def toString = f"My name is $name%s."
}

@SerialVersionUID(123L)
class Pet(var name: String, var species: String, var owner: Person)

trumanw

object HexStringUtil {
    
    // convert normal string to hex bytes string
    def string2hex(str: String): String = {
        str.toList.map(_.toInt.toHexString).mkString
    }
    
    // convert hex bytes string to normal string
    def hex2string(hex: String): String = {
        hex.sliding(2, 2).toArray.map(Integer.parseInt(_, 16).toChar).mkString