Scala partial functions and combination of partial functions

We have list of Partial Functions pf0-pf3, each has a personal domain area.

val sqv: Seq[Int] = (-5 to 20 by 1).toList

val pf0: PartialFunction[Int,Int] = {case i if i < 0 => 0}
val pf1: PartialFunction[Int,Int] = {case i if i >= 0 && i <= 5 => i + 10 }
val pf2: PartialFunction[Int,Int] = {case i if i > 5 && i <= 10 => i + 2 }
val pf3: PartialFunction[Int,Int] = {case i if i > 10  => i - 1 }

1) combine functions "manually"

val f = pf0 orElse pf1 orElse pf2 orElse pf3
val r1 = sqv map f

output:

val sqv: Seq[Int] = List(-5, -4, -3, -2, -1, 0,  1, 2, 3, 4, 5,           6, 7, 8, 9, 10,     11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
val r1:  Seq[Int] = List(0, 0, 0, 0, 0,          10, 11, 12, 13, 14, 15,  8, 9, 10, 11, 12,   10, 11, 12, 13, 14, 15, 16, 17, 18, 19)

2) combine with foldLeft

val sqFunc: Seq[PartialFunction[Int,Int]] = Seq(pf0, pf1, pf2, pf3)

val ff: PartialFunction[Int,Int]= sqFunc.foldLeft(sqFunc.head){
  case (acc,func) =>
   acc orElse func
}

val r2 = sqv map ff
r1 == r2

output:

val r2: Seq[Int] = List(0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
val res1: Boolean = true

3) combine with recursive function

def recurs (acc: PartialFunction[Int,Int], s: Seq[PartialFunction[Int,Int]]):
  PartialFunction[Int,Int] = {
   if (s.isEmpty) acc
   else recurs(acc orElse s.head, s.tail)
}

val fff = recurs(sqFunc.head, sqFunc.tail)
val r3 = sqv map fff
r2 == r3

output:

val fff: PartialFunction[Int,Int] = 

val r3: Seq[Int] = List(0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)

val res3: Boolean = true