I guess I formulated not precisely enough. I have not tried to accuse anybody of misusing. From books that I read I got a strong impression that the term &quot;functional programming&quot; as a term is about treating functions as the first-class entities (or even the only entities). The persistent data structures is orthogonal to this. But I guess I just have to accept that in the field it is a common speak to use &quot;functional algorithms&quot; to mean &quot;algorithms for persistent data structures&quot;.<p>Personally I see this as unfortunate as the persistence as a term IMO is much more precise. It also remains that one also needs GC and properly accounts its cost which this paper discuss a lot.