find first match in scala nested for loops

findFirst.scala

val data = (1 to 10).toSeq.map{i => (0 to i).map{_.toString}.toSeq}

val iters = for {
  sub <- data.iterator
  d <- sub.iterator
} yield d

val r = iters.find{x =>
  println(s"checking $x")
  x == "6"
}

//of course, no need for tmp var
(for {
  sub <- data.iterator
  d <- sub.iterator
} yield d).find{x => println(s"checking $x"); x == "6"}

//outputs:
checking 0
checking 1
checking 0
checking 1
checking 2
checking 0
checking 1
checking 2
checking 3
checking 0
checking 1
checking 2
checking 3
checking 4
checking 0
checking 1
checking 2
checking 3
checking 4
checking 5
checking 0
checking 1
checking 2
checking 3
checking 4
checking 5
checking 6

r: Option[String] = Some(6)



(for {
  sub <- data.iterator
  d <- sub.iterator
} yield d).find{x => println(s"checking $x"); x == "6"}