Scala : headOption

Having started on functional programming from JavaScript, after transforming and filtering elements in a list/iterator, the approach that I tried to extract the final filtered value out of the iterator was to try reduce operations. Instead, what I needed was the headOption method.

A simple example of transforming a list and extracting one value out, and additionally being able to specify a default value if nothing is left after the filtering exercise.

println(List(1,2,3)
   .map(_*2)
   .filter(_%3 ==0)
   .headOption
   .getOrElse(100)
   )
6

If we had started off with a list that would filter out everything, then we should get the default of 100.

println(List(1,2)
   .map(_*2)
   .filter(_%3 ==0)
   .headOption
   .getOrElse(100)
   )
100