Unit used in Scala Book without an explanation

[marksmithson]

In the Scala book, Unit is used in the Sample Pizza class example on this page https://docs.scala-lang.org/overviews/scala-book/enumerations-pizza-class.html.

This has not previously been explained. Perhaps it could be described on the previous page in the section about method return types. https://docs.scala-lang.org/overviews/scala-book/methods-first-look.html

I looked it up and found this - https://www.scala-lang.org/api/2.13.3/scala/Unit.html. I "think" it means that the return type is equivalent to a Javascript void.

[som-snytt]

This is solved in the "new version" by not using mutable data.

https://docs.scala-lang.org/scala3/book/domain-modeling-fp.html#modeling-the-data

The old version concludes, "hopefully it’s not too much to throw at you at one time." An alternate fix would confess that they haven't explained Unit yet.