Is there any advantage to definining a val over a def in a trait?

Question

In Scala, a val can override a def, but a def cannot override a val.

So, is there an advantage to declaring a trait

Answer 1

The difference is mainly that you can implement/override a def with a val but not the other way around. Moreover val are evaluated only once and def are evaluated every time they are used, using def in the abstract definition will give the code who mixes the trait more freedom about how to handle and/or optimize the implementation. So my point is use defs whenever there isn't a clear good reason to force a val.