Sample code for the Ironhack Meetup: Intro to scala for Ruby devs

ironhack-meetup-samples.scala

package com.marimon.meetup

object Naive extends App {

  def parse(s: String): Int = s.toInt
  def div(in: Int): Int = 16 / in
  def sqrt(in: Int): Double = Math.sqrt(in)


  val values = List("4", "2", "-4", "0", "asdf")

  values.map {
    input =>
      val x = parse(input)
      val y = div(x)
      val z = sqrt(y)
      z // this is like 'return z' but return is not necessary
  } foreach println

}

object Naive2 extends App {

  def parse(s: String): Int = s.toInt
  def div(in: Int): Int = 16 / in
  def sqrt(in: Int): Int = Math.sqrt(in).toInt

  val values = List("4", "2", "-4", "0", "asdf")

  values.foreach {
    input =>
      try {
        val x = parse(input)
        val y = div(x)
        val z = sqrt(y)
        println(z) /// <-- is that a valid result always?
      } catch {
        case x: NumberFormatException => println("Number format Exception: " + x.getMessage) // concat string
        case x: ArithmeticException => println(s"Arythmetic Exception: ${x.getMessage}") // interpolate strings
      }
  }

}


object Railways extends App {

  import scala.util.{Failure, Success, Try}
  def parse(s: String): Try[Int] = Try(s.toInt)
  def div(in: Int): Try[Int] = Try(16 / in)
  def sqrt(in: Int): Try[Int] =
    if (in >= 0) {
      Success(Math.sqrt(in).toInt)
    }
    else {
      Failure(new IllegalArgumentException("Can't sqrt negative values."))
    }

  val values = List("4", "2", "-4", "0", "asdf")

  // the type of the variable is already telling me something may
  // be wrong with each individual item of the 'results' list.
  val results: List[Try[Int]] = values.map {
    input =>
      for {
        x <- parse(input)
        y <- div(x)
        z <- sqrt(y)
      } yield {
        z
      }
  }
  
  results.foreach(println)
}