(#20684) Add array comparison functions, difference, intersection and union.

Included is code, tests and documentation for the difference, intersection
and union functions for comparing arrays.

1 files changed, 33 insertions, 0 deletions

diff --git a/README.markdown b/README.markdown
index 7b45b17..8d07a82 100644
--- a/README.markdown
+++ b/README.markdown
@@ -195,6 +195,18 @@ Would return: ['a','c']
 
 - *Type*: rvalue
 
+difference
+----------
+This function returns the difference between two arrays.
+The returned array is a copy of the original array, removing any items that
+also appear in the second array.
+
+*Examples:*
+
+    difference(["a","b","c"],["b","c","d"])
+
+Would return: ["a"]
+
 dirname
 -------
 Returns the `dirname` of a path.
@@ -416,6 +428,16 @@ Would return: {'a'=>1,'b'=>2,'c'=>3}
 
 - *Type*: rvalue
 
+intersection
+-----------
+This function returns an array an intersection of two.
+
+*Examples:*
+
+    intersection(["a","b","c"],["b","c","d"])
+
+Would return: ["b","c"]
+
 is_array
 --------
 Returns true if the variable passed to this function is an array.
@@ -868,6 +890,17 @@ Returns the type when passed a variable. Type can be one of:
 
 - *Type*: rvalue
 
+union
+-----
+This function returns a union of two arrays.
+
+*Examples:*
+
+    union(["a","b","c"],["b","c","d"])
+
+Would return: ["a","b","c","d"]
+
+
 unique
 ------
 This function will remove duplicates from strings and arrays.