how to find the max value in an IntList? - list

Question

I'm writing a function which will find the largest element in an IntList. I know how to do this in Java, but can't understand how to do this at Scala.
I made it, Here is what I have so far, I think this should be it.
abstract class IntList
case class Nil() extends IntList
case class Cons(h: Int, t: IntList) extends IntList
object ListFuns {
// return the maximum number in is
// return the maximum number in is
def maximum(is: IntList): Int = is match {
case Nil() => 0
case list => max(head(is), tail(is))
}
def head(l : IntList) : Int = l match {
case Nil() => 0
case Cons(e,tail) => e
}
def tail(l : IntList) : IntList = l match {
case Nil() => Nil()
case Cons(e,tail) => tail
}
def max(n : Int, l : IntList) : Int = l match {
case Nil() => n
case l => {
val h = head(l)
var champ = 0
if(n > h) {
champ = n
n
}
else{
champ = h
h
}
if(tail(l) == Nil()){
champ
}
else{
max(champ, tail(l))
}
}
}
}

Answer 1

Pattern matching would make it much shorter :
def maximum(l: IntList) : Int = l match {
case Cons(singleValue, Nil) => singleValue
case Nil() => // you decide, 0, the min value of ints, throw....
case Cons(head, tail) =>
val maxOfTail = maximum(tail)
if(maxOfTail > head) maxOfTail else head
}
minor notes:
you can change case class Nil() to case object Nil
the last two lines should be just head max maximum(tail), or head.max(maximum(tail)), whichever you are more comfortable with (they are the same thing).
This is just a starting point, as you learn further, you will find that my method not being tail-recursive is not too good. You might also consider whether you could return an Option to account for the empty list case. Also, notice that implementation of maximum, minimum, sum, product... are very similar, and try to factor that out.