How to append or prepend an element to a tuple in Scala

Question

I have a tuple and want to add an element without loosing type safety. This is what I want to achieve:

val tuple = ("", 1, 1f) // (String, Int, Float)

val newTuple:(String, Int, Float, Double) = tuple :+ 1d

Answer 1

It's worth noting that you can also write a code generator for this in a few lines:

val tupadd = for (n <- 2 to 20) yield {
  val t = (0 until n).map(i => ('A'+i).toChar).mkString(", ")
  val u = ('A'+n).toChar
  val i = (0 until n).map(i => "x._"+(i+1)).mkString(", ")
  List(
    s"implicit class TupOps$n[$t](val x: ($t)) extends AnyVal {",
    s"  def :+[$u](y: $u) = ($i, y)",
    s"  def +:[$u](y: $u) = (y, $i)",
    "}"
  ).mkString("\n")
}

Print these out, stick 'em in a file, and you're good to go:

scala> implicit class TupOps2[A, B](val x: (A, B)) extends AnyVal {
     |   def :+[C](y: C) = (x._1, x._2, y)
     |   def +:[C](y: C) = (y, x._1, x._2)
     | }
defined class TupOps2

scala> (1,"salmon") :+ true
res15: (Int, String, Boolean) = (1,salmon,true)