Show root node in seq of Trie

Before, if you did a lookup in a trie and then did a seq of the result,
you would get all of the children of the node that you looked up, but
you wouldn't get the value of the node itself.

This was nice when I was only getting children of the root node
because the root node never had a value and I didn't want it.

But I think it makes more since to always include the root node.
If it's not wanted, filter it out at the application level.

README.org

@@ -50,6 +50,7 @@ But there's a couple cool Trie-specific functions.
 #+begin_src clojure :results none :session usage-example
 (trie/lookup loosely-packed-trie "do")
 ;; => {[\g] :dog, [\t] :dot}
+(seq (trie/lookup loosely-packed-trie "do"))
 #+end_src
 
 `children` returns the direct children of a node.
@@ -95,12 +96,12 @@ Here's a similar example to that above, but with values that we can tightly pack
     v
     (if (zero? v) nil v)))
 
-(def loosely-packed-trie
+(def tight-ready-loosely-packed-trie
   (trie/make-trie '(1 2 3) 123 '(1 2 1) 121 '(1 2 2) 122 '(1 3 1) 131))
 
 (def tightly-packed-trie
   (tpt/tightly-packed-trie
-   loosely-packed-trie
+   tight-ready-loosely-packed-trie
    encode-fn
    decode-fn))
 

examples/markov_language_model.clj

@@ -236,7 +236,7 @@
   )
 
 (defn value-encode-fn [v]
-  (if (= v ::tpt/root)
+  (if (and (number? v) (zero? v))
     (encoding/encode 0)
     (byte-array
      (concat (encoding/encode (:id v))
@@ -245,7 +245,7 @@
 (defn value-decode-fn [byte-buffer]
   (let [id (encoding/decode byte-buffer)]
     (if (zero? id)
-      {:id :root}
+      {:id id}
       {:id id
        :count (encoding/decode byte-buffer)})))
 

src/com/owoga/tightly_packed_trie.clj

@@ -38,12 +38,12 @@
             (.limit ~byte-buffer original-limit#)
             (.position ~byte-buffer original-position#)))))
 
-(defn trie->depth-first-post-order-traversable-zipperable-vector
-  ([path node decode-value-fn]
+(defn -trie->depth-first-post-order-traversable-zipperable-vector
+  [path node decode-value-fn]
   (vec
    (map
     (fn [child]
-       [(trie->depth-first-post-order-traversable-zipperable-vector
+      [(-trie->depth-first-post-order-traversable-zipperable-vector
         (conj path (.key child))
         child
         decode-value-fn)
@@ -54,7 +54,21 @@
         (clojure.lang.MapEntry.
          (conj path (.key child))
          (decode-value-fn (.byte-buffer child))))])
-     (trie/children node)))))
+    (trie/children node))))
+
+(defn trie->depth-first-post-order-traversable-zipperable-vector
+  [path node decode-value-fn]
+  (let [byte-buffer (.byte-buffer node)
+        val (wrap-byte-buffer
+             byte-buffer
+             (.limit byte-buffer (.limit node))
+             (.position byte-buffer (.address node))
+             (decode-value-fn byte-buffer))]
+    [(-trie->depth-first-post-order-traversable-zipperable-vector
+      path
+      node
+      decode-value-fn)
+     (clojure.lang.MapEntry. path val)]))
 
 (defn rewind-to-key [bb stop]
   (loop []

src/com/owoga/trie.clj

@@ -1,15 +1,24 @@
 (ns com.owoga.trie
   (:require [clojure.zip :as zip]))
 
-(defn trie->depth-first-post-order-traversable-zipperable-vector
+(defn -trie->depth-first-post-order-traversable-zipperable-vector
   ([path node]
    (vec
     (map
      (fn [[k v]]
-       [(trie->depth-first-post-order-traversable-zipperable-vector (conj path k) v)
+       [(-trie->depth-first-post-order-traversable-zipperable-vector (conj path k) v)
         (clojure.lang.MapEntry. (conj path k) (.value v))])
      (.children- node)))))
 
+(defn trie->depth-first-post-order-traversable-zipperable-vector
+  [path node]
+  (if (.value node)
+    [(-trie->depth-first-post-order-traversable-zipperable-vector
+      path node)
+     (clojure.lang.MapEntry. path (.value node))]
+    (-trie->depth-first-post-order-traversable-zipperable-vector
+     path node)))
+
 (defn depth-first-post-order-traversable-zipperable-vector->trie
   [cls [children [key node]]]
   (sorted-map

test/tightly_packed_trie_test.clj

@@ -18,15 +18,6 @@
       nil
       v)))
 
-(comment
-  (let [t (->> '([1 3] 13 [1] 1 [1 2] 12)
-               (apply trie/make-trie)
-               (#(tpt/tightly-packed-trie % value-encode-fn value-decode-fn)))
-        bb (.byte-buffer t)]
-    (trie/lookup t [1 2]))
-
-  )
-
 (deftest tightly-packed-trie-tests
   (let [empty-trie (-> (trie/make-trie)
                        (#(tpt/tightly-packed-trie % value-encode-fn value-decode-fn)))
@@ -70,7 +61,8 @@
                [[1 2]   nil]
                [[1 3 1] 131]
                [[1 3]   nil]
-               [[1]     nil])
+               [[1]     nil]
+               [[]      nil])
              (seq initialized-trie))))))
 
 (comment