London Scala User Group Pizza Calculator

pizza-calculator.scala

/** This app calculates the number of pizzas needed for each
  * London Scala event.
  *
  * Meat, vegetarian and vegan pizzas are all a Dominos Large
  * size. Gluten-free pizzas come in a single small size.
  *
  * You can run this locally with:
  * 
  * > scala https://gist.github.com/zainab-ali/231e3ded6e8241d11e3927f9521bc0cc -- <numberOfSignupsOnMeetupDotCom>
  * 
  * For example:
  * > scala https://gist.github.com/zainab-ali/231e3ded6e8241d11e3927f9521bc0cc -- 70
  */

/** This fraction of people who sign up show up. */
val attendanceRate: Double = 0.6

/** We assume Large Dominos pizzas. These each have 10 slices. */
val slicesPerPerson: Double = 4
val slicesPerPizza: Double = 10

/** Our attendees have these dietary preferences. */
val fractionOfMeat: Double = 0.5
val fractionOfVegetarian: Double = 0.4
val fractionOfVegan: Double = 0.1

enum Flavour(val fraction: Double) {
  case Meat extends Flavour(0.45)
  case Vegetarian extends Flavour(0.4)
  case Vegan extends Flavour(0.1)
  case VeganGlutenFree extends Flavour(0.05)
}

case class PizzaCount(flavour: Flavour, count: Int)

@main def calculatePizza(signups: Int) = {

  val numberOfPeople = attendanceRate * signups
  val numberOfSlices = numberOfPeople * slicesPerPerson

  val meatSlices = numberOfSlices * fractionOfMeat
  val vegetarianSlices = numberOfSlices * fractionOfVegetarian
  val veganSlices = numberOfSlices * fractionOfVegan

  val counts = Flavour.values.toList.map { flavour =>
    val numberOfPizzas = Math.ceil(numberOfSlices * flavour.fraction / slicesPerPizza)
    PizzaCount(flavour, numberOfPizzas.toInt)
  }

  counts.foreach(println)
}