No, hash is fine here and faster, input is sorted anyway so there is …

…no place that needs to assume an alphabetical order, so this was not an issue. Doc also updated.

docs/nal.deriver.normalization.html

@@ -2923,13 +2923,13 @@
       ['-- (sort-commutative (second conclusions))]
       (let [f (first conclusions)]
         (if (commutative-ops f)
-          (vec (conj (sort-by str (drop 1 conclusions)) f))
+          (vec (conj (sort-by hash (drop 1 conclusions)) f))
           conclusions)))
     conclusions))</pre></td></tr><tr><td class="docs"><p>the union set operation for extensional and intensional sets</p>
 
 <p>https://gist.github.com/TonyLo1/a3f8e05458c5e90c2e72</p>
 </td><td class="codes"><pre class="brush: clojure">(defn union
-  ([c1 c2] (sort-by str (set (concat c1 c2))))
+  ([c1 c2] (sort-by hash (set (concat c1 c2))))
   ([op c1 c2] (vec (conj (union c1 c2) op))))</pre></td></tr><tr><td class="docs"><p>the difference set operation for extensional and intensional sets</p>
 </td><td class="codes"><pre class="brush: clojure">(defn diff
   ([c1 c2] (into '() (set/difference (set c1) (set c2))))

docs/uberdoc.html

@@ -3406,13 +3406,13 @@
       ['-- (sort-commutative (second conclusions))]
       (let [f (first conclusions)]
         (if (commutative-ops f)
-          (vec (conj (sort-by str (drop 1 conclusions)) f))
+          (vec (conj (sort-by hash (drop 1 conclusions)) f))
           conclusions)))
     conclusions))</pre></td></tr><tr><td class="docs"><p>the union set operation for extensional and intensional sets</p>
 
 <p>https://gist.github.com/TonyLo1/a3f8e05458c5e90c2e72</p>
 </td><td class="codes"><pre class="brush: clojure">(defn union
-  ([c1 c2] (sort-by str (set (concat c1 c2))))
+  ([c1 c2] (sort-by hash (set (concat c1 c2))))
   ([op c1 c2] (vec (conj (union c1 c2) op))))</pre></td></tr><tr><td class="docs"><p>the difference set operation for extensional and intensional sets</p>
 </td><td class="codes"><pre class="brush: clojure">(defn diff
   ([c1 c2] (into '() (set/difference (set c1) (set c2))))

src/nal/deriver/normalization.clj

@@ -69,14 +69,14 @@
       ['-- (sort-commutative (second conclusions))]
       (let [f (first conclusions)]
         (if (commutative-ops f)
-          (vec (conj (sort-by str (drop 1 conclusions)) f))
+          (vec (conj (sort-by hash (drop 1 conclusions)) f))
           conclusions)))
     conclusions))
 
 ;https://gist.github.com/TonyLo1/a3f8e05458c5e90c2e72
 (defn union
   "the union set operation for extensional and intensional sets"
-  ([c1 c2] (sort-by str (set (concat c1 c2))))
+  ([c1 c2] (sort-by hash (set (concat c1 c2))))
   ([op c1 c2] (vec (conj (union c1 c2) op))))
 
 (defn diff