循环

object object00 {
  def main(args:Array[String]):Unit={
     for(i <- 1 to 20 by 2){
       println(i)
    }
  }
}

循环守卫

object basic20 {
  def main(args:Array[String]):Unit={
    for(j <- 1 to 20; if(j%2==0);if(j%3==0)){
      println(j)
    }
  }

}

object basic21 {
  def main(args:Array[String]):Unit={
    var s = 0.0
    for (i <- 1 until 20) {
      if (i % 2 == 1) {
        s += 1.0 / i  // 奇数项加1/i
      } else {
        s -= 1.0 / i  // 偶数项减1/i
      }
    }
    println(s" s的值为 $s")
  }
}

class basic {
 def main(args:Array[String]):Unit={
   val rs = for(i <- 1 to 4) yield{
     i*2
   }
   println(rs)
   println(rs(0))
   println(rs(1))
   println(rs(2))
 }
}