emmettna

// porivided width * height 
// calculate the number of empty cells
// ex) [ ][ ][/]
//     [ ][/][ ]
//.    [/][ ][ ]
// 

// gcd : https://gist.github.com/emmettna/702d972126d381dcceb8d8122ba7893c
def calcEmptyCells(width: Int, heght: Int): Int = width + heght - (gcd(width, heght))

emmettna

import java.math.BigInteger

def gcd(left: Long, right: Long): Long = BigInteger.valueOf(left).gcd(BigInteger.valueOf(right)).longValue

emmettna

import cats.Applicative
import cats.effect.concurrent.Ref
import cats.implicits._
import cats.effect._

class InMemorySimpleCrud[F[_]: Applicative](ref: Ref[F, Map[String, Human]])
  extends SimpleCrud.Service[F] {
    override def add(human: Human): F[Unit] = 
      ref.update(_.updated(human.name, human))
    override def find(name: String): F[Option[Human]] = 

emmettna

final case class Human(name: String, age: Int)
trait SimpleCrud[F[_]] {
  val simpleCrudService: SimpleCrud.Service[F]
}
object SimpleCrud {
  trait Service[F[_]] {
    def add: F[Unit]
    def find(name: Name): F[Option[Human]]
  }
}

emmettna

val five = 5
five match {
  case v if v > 5 => ???
  case v if v == 5 => ???
  case v if v < 5 => ???
}
// more practical example
final case class FeeInquiry(user: UserId, amount: BigDecimal, currency: Currency)

val requestedFee: Option[FeeInquiry] = ???

emmettna

"1,2,3".split(",").toList match {
  case first :: second :: third :: Nil => "Counting Practice"
  case _ => throw new Exception("This is not what I expected")
}

emmettna

val list: List[Option[Int]] = List(Some(1), None, Some(2))
val result: List[Int]=list.map( numberOpt => numberOpt match {
  case Some(v) => v
  case None => 0
})

emmettna

final case class DummyCaseClass(value: Int)
val dummyCaseClassOpt = Option(DummyCaseClass(1))
dummyCaseClassOpt match {
  case Some(DummyCaseClass(v)) => v.toString
  case Some(_) => ???
  case None => ???
}
// equivalent
dummyCaseClassOpt match {
  case v: Some[DummyCaseClass] => v.toString

emmettna

val optionValue = Option(1)
optionValue match {
  case Some(v) => ???
  case None => ???
}

emmettna

final case class IntegerParser(value: Int)
val prasedInt = IntegerPraser(value = 1)
parsedInt match {
  case IntegerParser(value) => value.toString
  case _ => "Invalid Int"
}