commit 444e941ce068d17017cf8ef7b25543271eff133f
Author: Li Ellis Gallardo <lellisga@gmail.com>
Date:   Tue May 29 20:29:40 2012 -0500

    array.c: added method that verifies if an Array is part of another

diff --git a/array.c b/array.c
index 59572ec..da63e80 100644
--- a/array.c
+++ b/array.c
@@ -4686,6 +4686,26 @@ rb_ary_drop_while(VALUE ary)
 }
 
 /*
+ *  call-seq:
+ *     ary.part_of? other_ary   ->   bool
+ *
+ *  Array 'A' is part of another array 'B' if
+ *  each element from 'A' are included in 'B'
+ *
+ *  [ "a", "c" ].part_of? [ "a", "b", "c" ]    #=> true
+ *  [ "a", "d" ].part_of? [ "a", "b", "c" ]    #=> false
+ *  [].part_of []                              #=> true
+ *
+ */
+
+static VALUE
+rb_ary_part_of(VALUE ary1, VALUE ary2)
+{
+  ary2 = rb_ary_diff(ary1, ary2);
+  return rb_ary_empty_p(ary2);
+}
+
+/*
  * Arrays are ordered, integer-indexed collections of any object.
  * Array indexing starts at 0, as in C or Java.  A negative index is
  * assumed to be relative to the end of the array---that is, an index of -1
@@ -5020,6 +5040,7 @@ Init_Array(void)
     rb_define_method(rb_cArray, "take_while", rb_ary_take_while, 0);
     rb_define_method(rb_cArray, "drop", rb_ary_drop, 1);
     rb_define_method(rb_cArray, "drop_while", rb_ary_drop_while, 0);
+    rb_define_method(rb_cArray, "part_of?", rb_ary_part_of, 1);
 
     id_cmp = rb_intern("<=>");
     sym_random = ID2SYM(rb_intern("random"));
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index 1687589..68bd913 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -2184,4 +2184,18 @@ class TestArray < Test::Unit::TestCase
     a = [1,2,3]
     assert_raise(ArgumentError) { a.rotate!(1, 1) }
   end
+
+  def test_part_of?
+    assert_equal(true, [].part_of?([]))
+    a = [1, 3, 4]
+    b = [1, 2, 3, 4, 5]
+    assert_equal(true, a.part_of?(b))
+    assert_equal(false, b.part_of?(a))
+    a = %w( ant bat cat dog )
+    b = %w( dog cat bat ant )
+    assert_equal(true, a.part_of?(b))
+    assert_equal(true, b.part_of?(a))
+    assert_raise(TypeError) { a.part_of? 1 }
+    assert_raise(ArgumentError) { a.part_of?() }
+  end
 end