ScalaForComprehension.scala

package collections
import scala.collection.immutable

object ScalaForComprehension {

  case class Person(first: String, last: String)

  val persons: List[Person] = List(
    Person("Rupesh", "Raghavan"),
    Person("Roopa", "Rupesh"),
    Person("Rhea", "Rupesh"),
    Person("Reva", "Rupesh"))

  val result: List[String] = for {
    elem <- persons // generator
    first = elem.first // definition
    if (first.startsWith("Ru")) // filter
  } yield first


  val forPerson: List[String] = for {
    p <- persons
    firstName = p.first
    lastNam = p.last
    if (lastNam == "Rupesh")
  } yield firstName.toUpperCase

  val yieldForSeq: Seq[Int] = for (a <- 1 to 10) yield a //creates iterator
  val yieldForIndexed: IndexedSeq[Int] = for (a <- 1 to 10) yield a //creates iterator

  val resul23: List[String] = for (elem <- persons if (elem.last == "Rupesh")) yield elem.first


  // FlatMap map for comprehension
  //The for comprehension is a syntax shortcut to combine flatMap and map 

  val numbers = List(1,2)
  val chars = List('a','b')
  val colors = List("black", "white")

  val flatMapComp: List[String] = numbers
    .flatMap((number: Int) => chars.flatMap((char: Char) => colors.map((color: String) => number + "-"+ char+  "-" +color  )))

  val forComb: List[String] = for {
      number <- numbers
      char <- chars
      color  <- colors
  } yield number + "-"+ char+  "-" +color

  //List(1-a-black, 1-a-white, 1-b-black, 1-b-white, 2-a-black, 2-a-white, 2-b-black, 2-b-white)
  //List(1-a-black, 1-a-white, 1-b-black, 1-b-white, 2-a-black, 2-a-white, 2-b-black, 2-b-white)

  def main(args: Array[String]): Unit = {
//    println(result)
//    println(forPerson)
    println(flatMapComp)
    println(forComb)


  }

}