How to find the largest element in a list of integers recursively?

Question

I\'m trying to write a function which will recursively find the largest element in a list of integers. I know how to do this in Java, but can\'t understand how to do this at Sca

Answer 1

1. Folding can help:

   if(xs.isEmpty)
     throw new NoSuchElementException
   else
     (Int.MinValue /: xs)((max, value) => math.max(max, value))
   

2. List and pattern matching (updated, thanks to @x3ro)

   def max(xs:List[Int], defaultValue: =>Int):Int = {
     @tailrec
     def max0(xs:List[Int], maxSoFar:Int):Int = xs match {
       case Nil => maxSoFar
       case head::tail => max0(tail, math.max(maxSoFar, head))
     }
     if(xs.isEmpty)
       defaultValue
     else
       max0(xs, Int.MinValue)
   }
   

(This solution does not create Option instance every time. Also it is tail-recursive and will be as fast as an imperative solution.)