There are more real solutions which scale better, but in these toy problems it's hard to get to the meat of the problem. Sometimes the "existential antipattern"

There are more real solutions which scale better, but in these toy problems it's hard to get to the meat of the problem. Sometimes the "existential antipattern" is a good choice (see Oleg's finally tagless encoding of, say, the linear lambda calculus). Sometimes creative use of static structure can scale much more neatly than lists of concrete objects.