Review Math methods; fix broken kldivergence

- Fix Math.kldivergence (was calling self/each_with_index instead of
  array parameter — has been broken since it was written)
- 63 Math methods reviewed: 48 unique, 7 redirects, 4 safe clashes
  (log2 guarded, lgamma commented out, gcd/lcm different namespace)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: trans

HISTORY.md

@@ -137,6 +137,7 @@ Changes:
   * Fix Pathname#glob to wrap Ruby's built-in, adding symbol flag support.
   * Remove Pathname#empty? (built into Ruby).
   * Deprecate Pathname.null (use Pathname.new(File::NULL)).
+  * Fix `Math.kldivergence` (was broken — referenced `self` instead of array parameter).
   * Drop unused `test_files` directive from gemspec. (PR#301)
 
 

lib/standard/facets/math/kldivergence.rb

@@ -1,19 +1,20 @@
 module Math
 
-  # The Kullback-Leibler divergence from this array to that of +q+.
+  # The Kullback-Leibler divergence from distribution +p+ to distribution +q+.
+  #
+  # Both arrays must be the same size and represent probability distributions
+  # (values should be positive).
   #
   # NB: You will possibly want to sort both P and Q before calling this
   # depending on what you're actually trying to measure.
   #
   # http://en.wikipedia.org/wiki/Kullback-Leibler_divergence
   #
-  def self.kldivergence(array, q)
-    fail "Buggy."
-    fail "Cannot compare differently sized arrays." unless size = q.size
-    kld = 0
-    each_with_index { |pi,i| kld += pi*Math::log(pi.to_f/q[i].to_f) }
+  def self.kldivergence(p, q)
+    raise ArgumentError, "Cannot compare differently sized arrays." unless p.size == q.size
+    kld = 0.0
+    p.each_with_index { |pi, i| kld += pi * Math.log(pi.to_f / q[i].to_f) }
     kld
   end
 
 end
-