Question

In Java, with a java.util.SortedMap<Long,Object>, we can do something like:

sortedMap.headSet(13).clear()

to get rid of all the elements with keys < 13. I don’t see anything similar in clojure.core for clojure’s (sorted-map) (which I think is always a clojure.lang.PersistentTreeMap). The best I’ve come up with is something like this:

(let [clear-up-to 13
      sm (sorted-map 1 "aye" 2 "bee" 13 "em" 14 "en")]
      clear-keys (take-while #(< % clear-up-to) (keys sm))
  (apply dissoc sm clear-keys))

Am I missing something simpler?

Answer 1

Dissoc is the best you can do, but the take-while step should be replaced with subseq or rsubseq, as appropriate.