Some operations on tuples

[anatoliykmetyuk]

Blocked by pickling issues. Also, #7056 prevents using extension methods from the type class.

[anatoliykmetyuk]

Pickling issues in question: #7058

[nicolasstucki]

Here is an implementation of zip without using the Aux anti-pattern. It just needs a match type. Also note that the implementation uses safe casts to avoid the quadratic tuple copy of tail.

object App1 {

  type Zip[T1, T2] <: Tuple = (T1, T2) match {
    case (h1 *: t1, h2 *: t2) => (h1, h2) *: Zip[t1, t2]
    case (Unit, _) => Unit
    case (_, Unit) => Unit
    case _ => Tuple
  }

  def (t1: T1) zip [T1 <: Tuple, T2 <: Tuple](t2: T2): Zip[T1, T2] = {
    if (t1.size == 0 || t2.size == 0) ().asInstanceOf[Zip[T1, T2]]
    else Tuple.fromArray(t1.asInstanceOf[Product].productIterator.zip(t2.asInstanceOf[Product].productIterator).toArray).asInstanceOf[Zip[T1, T2]]
  }

  val x: (1, 2, 3) = (1, 2, 3)
  val y: (4, 5, 6) = (4, 5, 6)

  val z: ((1, 4), (2, 5), (3, 6)) = x.zip(y)

}

[anatoliykmetyuk]

Superseded by #7073