How do you make a binary search tree in Clojure?

Question

In Scheme, I can use define-struct to make a binary search tree, but how do you do it in Clojure?

Answer 1

The simplest way would be to use the tree that is already defined in language (every sorted-map is a tree really, if you just need different function to compare keys, use sorted-map-by).

;;define function for comparing keys
(defn compare-key-fn [key1 key2] (< key1 key2) )

;;define tree and add elements
(def my-tree
  (->                              ;;syntax sugar
    (sorted-map-by compare-key-fn) ;;this returns empty tree with given function to compare keys
    (assoc 100  "data for key = 100") ;;below we add elements to tree
    (assoc 2  "data for key = 2")
    (assoc 10 "data for key = 10")
    (assoc -2 "data for key = -1")))

;;accesing  elements by key
(prn "element for key 100 =" (my-tree 100))

;;"erasing" elements from tree - in reality, what we are really doing, is returning a new tree that contains all elements of the old one, except the element we've just erased.
(def my-new-tree
  (dissoc my-tree 2))

(prn my-new-tree) ;; to verify, that element 2 is "erased"