Question

I understand that the functional style prefers var or val List of a mutable, and I understand why, but I am thinking about purely time/space trade offs.

I am currently interfacing with a java library and have to write tons of non idomatic code in scala anyways..

Answer 1

Maybe several pointers can help you to understand, why there is not a so big penalty when you use immutable structure:

• The Performance characteristics table of the scala collections.
• Extreme Cleverness: Functional Data Structures in Scala (a quite long but so interesting video on immutable data structures)