[Scala] Many ways of passing x < 0 function into exists function (verbose version as first one). Each of them has the same meaning.

FunctionsCall.scala

def containsNeg1(nums: List[Int]) = nums.exists((x: Int) => x < 0)
def containsNeg2(nums: List[Int]) = nums.exists((x) => x < 0)
def containsNeg3(nums: List[Int]) = nums.exists(x => x < 0)
def containsNeg4(nums: List[Int]) = nums.exists(_ < 0)