scala_for_customed.scala

import scala.jdk.CollectionConverters._
import scala.util.chaining._

case class Myforable[A](v: List[A]):
  def foreach[T](f: A => T): Unit = v.foreach(f)

  def map[T](f: A => T): Myforable[T] = Myforable(v.map(f))

  def flatMap[T](f: A => Myforable[T]): Myforable[T] =
    val list: List[T] = v.map(f).map(_.v).flatten
    Myforable(list)

  def withFilter(f: A => Boolean): Myforable[A] = Myforable(v.filter(f))


object Main:
  def main(args: Array[String]): Unit = time {
    val m = Myforable(List("a", "b"))
    for it <- m do //need foreach method
      println(it)

    val m2 = for (it <- m) yield it + "_" // need map method
    println(m2)

    val m3 = for {
      it <- m // need flatMap method
      it2 <- m
    } yield it + "_" + it2
    println(m3)

    val m33 = m.flatMap(it => m.map(it2 => it + "_" + it2))
    println(m33)

    val m4 = for {
      it <- m // need withFilter method
      if it.chars().findFirst().orElse(0) > 'a'.toInt
      it2 <- m
    } yield it + "_" + it2
    println(m4)
  }