Clarify set intersection and union documentation

* array.c (rb_ary_and): clarify that set intersection returns the
  unique elements common to both arrays.

* array.c (rb_ary_or): clarify that union preserves the order from
  the given arrays.

- Most know what intersection means, but saying the operation
  excludes duplicates could be misleading ([1] & [1], duplicates
  excluded, might mean a result of []).
- Instead, saying intersection returns the unique elements common to both
  arrays is more concise and less ambiguous.
- The set union's documentation was incomplete in its describing
  preservation of order. Saying union preserves the order of the
  original array neglects the idea that the order of the elements
  in both arrays, as given, will be preserved.
- Instead, saying set union preserves the order from the given arrays (and
  adding an example) fully demonstrates the idea.

[Fix GH-1273] [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53958 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 4b02a6c976..52591cfaec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sun Feb 28 10:19:47 2016  Ryan T. Hosford  <tad.hosford@gmail.com>
+
+	* array.c (rb_ary_and): clarify that set intersection returns the
+	  unique elements common to both arrays.
+
+	* array.c (rb_ary_or): clarify that union preserves the order from
+	  the given arrays.
+
 Sat Feb 27 17:05:29 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* enc/unicode/case-folding.rb, casefold.h: Reducing size of TitleCase