Pair

A pair include 2 elements that is written (x, y) in Scala

Pairs can also be used as patterns: val (label, value) = pair 

Tuple

A tuple includes more than 2 elements

The fields of a tuple can be accessed with names _1, _2, …

Example

Write a function merge sort using pair and pair pattern

def msort(xs: List[Int]): List[Int] = {
 val n = xs.length/2
 if (n == 0) xs
 else {
  val (first, second) = xs splitAt(n)
  merge(msort(first), msort(second))
 }
}

def merge(xs: List[Int], ys: List[Int]): List[Int] = {
 (xs, ys) match {
   case (Nil, ys) => ys
   case (x :: xs1, Nil) => xs
   case (x :: xs1,  y :: ys1) =>
     if(x < y) x :: merge(xs1, y :: ys1)
     else y :: merge(x :: xs1, ys1)
 }
}