jiamingd

import scala.collection.mutable
import scala.io.Source
import scala.util.Try

/*
Sample csv:
user_id,age,favorite_color
0,5,cyan
1,5,gray
2,22,green

jiamingd

//http://aperiodic.net/phil/scala/s-99/, p26
// In how many ways can a committee of 3 be chosen from a group of 12 people? 
//We all know that there are C(12,3) = 220 possibilities (C(N,K) denotes the well-known binomial coefficient). 
//For pure mathematicians, this result may be great. But we want to really generate all the possibilities.


import scala.annotation.tailrec

val interested = Seq('a','b', 'c', 'd','e', 'f', 'g','h', 'i')

jiamingd

trait Show[A] {
  def doShow(input : A) : String
}

// Value class apporach need more tune up
// Value class: Goal is to avoid a runtime overhead
//implicit class LetShowable[A](val a: A) extends AnyVal{
//  def letShow(implicit sh: Show[A]) = sh.doShow(a)
//}

jiamingd

trait Pet {
  def name : String
}

trait Renamable[A] {
  def rename( a: A, newName: String): A
}

case class Fish(name: String, age: Int)
object Fish {

jiamingd

case class Car(color: String, size : Int, door : Int){
  def this(door : Int) = this("silver", 6, door)
}

object Car{
  def apply(door : Int ) = new Car(door)
}

val coupe = Car(2)
val car = Car("red", 8, 4)

jiamingd

case class MyFunctor[K](contextValue: K) {
   def map[T](f: K => T) : MyFunctor[T]= {
     MyFunctor( f(this.contextValue) )
  }
}

case class MyMonad[K](contextValue : K) {
  def flatMap[T](f: K => MyMonad[T]) : MyMonad[T] = {
    println(s"flatMap called: $contextValue ")
    f(this.contextValue)

jiamingd

object HLists {

  trait HList {
    type ConResult[A] <: HList

    def ::[A](a: A): ConResult[A]
  }

  case class HCol[H, T](h: H, t: T) extends HList {
    override type ConResult[A] = HCol[A, HCol[H, T]]

jiamingd

object TeathCleans {
  trait TeathClean {
    def cleanTeath
  }
  trait SonicTeathClean extends TeathClean {
    override def cleanTeath = {
      println("supersonic cleaning")
    }
  }
  trait NormalBrushTeathClean extends TeathClean {