filter and report multiple predicates

Question

This is a kind of cosmetic Scala question. A list with objects needs to be filtered on the objects\' attributes. I need to report if the first check on the attribute results

Answer 1

The following code is a slight modification from this SO answer from Rex Kerr.

implicit class KestrelPattern[A](private val repr: A) extends AnyVal {
  def tee[B](f: A => B) = { f(repr); repr } // B is thrown away (Unit)
}

He called it tap. I chose tee because of the similarity to the unix tee command.

Usage:

scala> List[Int](3,5,7).tee{x => if (x.isEmpty) println("ERROR")}.sum
res42: Int = 15

scala> List[Int]().tee{x => if (x.isEmpty) println("ERROR")}.sum
ERROR
res43: Int = 0