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import cats.effect._
import fs2._
import scala.concurrent.duration._
import cats.effect.std._

// FS2 cats.effect.Queue example using flatMap or for comprehension
// Both streams emit nothing, but are effectful, communicating via the queue and updating a sum via the ref

object Fs2Queues extends IOApp.Simple {

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import MyErrsIO.Controller.{Request, postTransfer}
import MyErrsIO.Models.Account
import cats.data.Validated.{Invalid, Valid}
import cats.data.{EitherT, OptionT, Validated, ValidatedNec}
import cats.effect._
import cats.implicits._

import scala.util.control.NonFatal

// A simple example of cat-effect and error handling, with MonadTransformers

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import cats._

object TreeFunctorExample {

  def main(args: Array[String]): Unit = {

    sealed trait Tree[+T]
    case class Leaf[+T](value: T) extends Tree[T]
    case class Branch[+T](value: T, left: Tree[T], right: Tree[T]) extends Tree[T]

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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