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object Intersect extends App{

  import scala.annotation.tailrec

  // finds the elements shared by 2 lists, FP style, recursively
  // O(n log n)

  @tailrec
  def scan(x: List[Int], y: List[Int], out: List[Int] = List.empty[Int]): List[Int] =
    (x, y) match {

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import scala.annotation.tailrec

/** width by height grid
 starting top left
 how many ways to travel to bottom right?
 can only go right or down
 3 methods shown
**/
object WaysToTraverseGrid extends App{

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// NumberToWords converts an Int into English words

object NumberToWords extends App{

  val num2Word=Map((0, "Zero"), (1, "One"),
                  (2, "Two"), (3, "Three"),
                  (4, "Four"), (5, "Five"),
                  (6, "Six"), (7, "Seven"),
                  (8, "Eight"), (9, "Nine"),
                  (10, "Ten"), (11, "Eleven"),

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// Top and bottom N max/min items from an Array, with no need to sort

object TopBottomN extends App {

  def bottomN(a: Array[Int], n: Int): Array[Int] = {
    val smallestVals = Array.fill(n)(Int.MaxValue)

    a.foreach { number =>
      var inserted=false
      (n - 1 to 0 by -1).foreach { pos =>

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def css = Action {
    val css: TxtFormat.Appendable =views.txt.css()
    Ok(css).as("text/css")
  }
  
inside HTML

  <link rel="stylesheet" href="@routes.HomeController.css()"/>
  

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  implicit object NullBooleanReads extends Reads[Boolean] {
    def reads(json: JsValue): JsSuccess[Boolean] = json match {
      case JsBoolean(b) => JsSuccess(b)
      case _ => JsSuccess(false)
    }
  }

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import cats._
import cats.implicits._


// Cats SemigroupK vs Semigroup

object CatsSemigroupK extends App {

  // semigroupK doesn't care about contents

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import cats._
import cats.implicits._

// Example usage of Cats Flatmap

object CatsFlatmap extends App {

  val listFlatMap=FlatMap[List]

  val li=List(1,2,3)

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import cats._
import cats.implicits._

// Cats Apply, does cartesian maps, extends Functor and Semigroupal (which does cartesian joins, unlike pairwise Align)

object CatsAp extends App {

  val apOption=Apply[Option]

  val option1: Option[(Int, Int)] =apOption.product(Option(1), Option(2))

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// take out the + and see the last few lines fail as doit then only takes Animal, and not its subtypes
// we output A, so + is fine, we are covariant
sealed trait ThisThatValue[+A]

object ThisThatValue {
  final case class This[+A](value: A) extends ThisThatValue[A]
  final case class That[+A](value: A) extends ThisThatValue[A]
}