Adding Array Elements in Scala

So i’m learning Scala and tried to create a vector class based on array and create an addition and substraction operators to add 2 vectors. This is what I did so far. Can anyone help to figure out how to make it so that when I add to vectors of different length, it adds “0” to the array with the shorter length so that it’s length is equal to the one with the bigger length? Like add (1, 2) to (1, 2, 3) should return (2, 4, 3)

class Wektor(private val s: Array[Double]){
        class LengthNotEqualException(msg:String) extends Exception(msg)
        def get(index: Int):Double= s(index)
        def +(that: Wektor):Wektor=
          if(this.s.length != that.s.length)
                  throw new LengthNotEqualException("Wektory roznej dlugosci")
          else
          {
            val temp= new Array[Double](this.s.length)
            var i:Int= 0
                for(i <- 0 until this.s.length)
            {
                temp(i)= this.s(i) + that.get(i)
            }
            new Wektor(temp)    // zwraca nowy Wektor będący sumą danych wektorów
          }
        def -(that: Wektor):Wektor=
          if(this.s.length != that.s.length)
                  throw new LengthNotEqualException("Wektory roznej dlugosci")
          else
          {
            val temp= new Array[Double](this.s.length)
            var i= 0
                for(i <- 0 until this.s.length)
            {
                temp(i)= this.s(i) - that.get(i)
            }
            new Wektor(temp)    // zwraca nowy Wektor będący różnicą danych wektorów
          }
        def *+(that:Wektor):Double=
          if(this.s.length != that.s.length)
                  throw new LengthNotEqualException("Wektory roznej dlugosci")
          else
                {
                  var result:Double= 0
                  var i:Int = 0
                  for(i <- 0 until this.s.length)
                  {
                result= result + this.s(i) * that.get(i)
                  }
                  result        // zwracany iloczyn skalarny
                }
        override def toString():String={
          var result:String="Wektor: ["
          var i:Int= 0
          for(i <- 0 until this.s.length)
          {
                  result= result + this.s(i) + " "
          }
          result = result + "]"
          result        // zwracana wartosc
        }
}

val test= new Wektor(Array[Double](1, 2, 3,5))
val test2= new Wektor(Array[Double](2, 2, 2))
val suma= test + test2
val roznica= test - test2
val iloczyn= test *+ test2
println(suma)
println(roznica)
println(iloczyn)