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fancellu / Intersect.scala
Created May 28, 2021
Finds the elements shared by 2 lists, FP style, recursively
View Intersect.scala
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 {
@fancellu
fancellu / WaysToTraverseGrid.scala
Last active May 13, 2021
3 Methods to find how many Ways To Traverse a Grid
View WaysToTraverseGrid.scala
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{
@fancellu
fancellu / NumberToWords.scala
Created May 12, 2021
NumberToWords converts an Int into English words
View NumberToWords.scala
// 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"),
@fancellu
fancellu / TopBottomN.scala
Last active May 9, 2021
// Top and bottom N max/min items from an Array, with no need to sort
View TopBottomN.scala
// 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 =>
@fancellu
fancellu / scala_play_css_tip.txt
Last active Feb 25, 2021
Tip to have CSS with Play Twirl, if SASS isn't powerful enough for you...
View scala_play_css_tip.txt
def css = Action {
val css: TxtFormat.Appendable =views.txt.css()
Ok(css).as("text/css")
}
inside HTML
<link rel="stylesheet" href="@routes.HomeController.css()"/>
@fancellu
fancellu / NullBooleanReads.scala
Created Aug 27, 2020
NullBooleanReads for play-json. Sometimes dirty json has a boolean of "null". This takes it to mean false
View NullBooleanReads.scala
implicit object NullBooleanReads extends Reads[Boolean] {
def reads(json: JsValue): JsSuccess[Boolean] = json match {
case JsBoolean(b) => JsSuccess(b)
case _ => JsSuccess(false)
}
}
@fancellu
fancellu / CatsSemigroupK.scala
Created Jun 10, 2020
Cats SemigroupK vs Semigroup
View CatsSemigroupK.scala
import cats._
import cats.implicits._
// Cats SemigroupK vs Semigroup
object CatsSemigroupK extends App {
// semigroupK doesn't care about contents
@fancellu
fancellu / CatsFlatmap,scala
Created Jun 10, 2020
Example usage of Cats FlatMap
View CatsFlatmap,scala
import cats._
import cats.implicits._
// Example usage of Cats Flatmap
object CatsFlatmap extends App {
val listFlatMap=FlatMap[List]
val li=List(1,2,3)
@fancellu
fancellu / CatsAp.scala
Created Jun 9, 2020
Cats Apply, does cartesian maps, extends Functor and Semigroupal (which does cartesian joins, unlike pairwise Align)
View CatsAp.scala
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))
@fancellu
fancellu / CovariantExample.scala
Created May 29, 2020
Scala example of declaration side Type Covariance
View CovariantExample.scala
// 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]
}