perf improvement in sorted-numbers?

Engelberg · Engelberg · commit 67b2e2a38be6 · 2014-07-19T15:00:10.000-07:00
sorted-numbers? is called once at the beginning of the permutations
function in order to determine which version of the permutations
algorithm to use -- a more efficient algorithm can be chosen if the
numbers are already sorted.  Since this function is only called once,
improving its performance will have a negligible effect on the overall
performance of permutations.  But this is an improvement, so why not?
diff --git a/src/main/clojure/clojure/math/combinatorics.clj b/src/main/clojure/clojure/math/combinatorics.clj
@@ -172,9 +172,9 @@ In prior versions of the combinatorics library, there were two similar functions
 
 (defn- sorted-numbers?
   "Returns true iff s is a sequence of numbers in non-decreasing order"
-  [s]
+  [s]
   (and (every? number? s)
-       (every? (partial apply <=) (partition 2 1 s))))
+       (or (empty? s) (apply <= s))))
 
 (defn- multi-perm
   "Handles the case when you want the permutations of a list with duplicate items."
