Question

In the Java/C world, people often use enums. If I’m using a Java library which using enums, I can convert between them and keywords, for example, using (. java.lang.Enum valueOf e..., (aget ^"[Ljava.lang.Enum;" (. e (getEnumConstants)) i), and some reflection. But in the Clojure world, do people ever need anything like an enum (a named integer) ? If not, how is their code structured that they don’t need them ? If yes, what’s the equivalent ? I sense I’m really asking about indices (for looping), which are rarely used in functional programming (I’ve used map-indexed only once so far).

Answer 1

For almost all the Clojure code I have seen keywords tend to be used instead of Enums they are name-spaced and have all the other useful properties of keywords while being much easier to write. They are not an exact standin because they are more dynamic (as in dynamic typing) than Java enums

as for indexing and looping I find it more idiomatic to map over a sequence of keywords:

(map do-stuff [:a :b :c :d] (range)) 

than to loop over the values in an enumeration, which I have yet to find an example of in Clojure code, though an example very likely exists 😉