Hamming distance in Scala
Strings have a .zip() method; calling .toList() is superfluous.

Instead of .filter(…) and .length(), use .count(…).

I'm not a fan of the name current, which has a connotation of iteration.

Avoid omitting braces with if statements.  If you want to do so, put the body on the same line to avoid accidents.

object Hamming {
  def compute(s1: String, s2: String): Int = {
    if (s1.length != s2.length) throw new IllegalArgumentException()
    s1.zip(s2).count(pair =&gt; pair._1 != pair._2)
  }  
}