Create a sorted-map of coordinates

Question

I wrote a little function to create a sorted-map with vectors of coordinates as keys and an empty map as a default value:

(defn empty-board [rows cols]
  (into (sorted-map) 
        (for [x (range cols) y (range rows)]
            [[x y] {}])))

Is there is a more idiomatic way of achieving this?

Answer 1

Yes, this is the right way to do it.

Many Clojure programs do not bother with creating empty maps. The absence of a value or nil behave like an empty map. For example (assoc nil :foo :bar) returns {:foo :bar}. You may be able to initialize to an empty sorted-map, and only assoc-in novelty as you need it ... depending on your logic.