diff --git a/array.c b/array.c
index 5a8d8dc..2c8944e 100644
--- a/array.c
+++ b/array.c
@@ -1490,6 +1490,39 @@ rb_ary_rindex(int argc, VALUE *argv, VALUE ary)
     return Qnil;
 }
 
+/*
+ *  call-seq:
+ *     ary.has_index?(idx)    -> true or false
+ *     ary.index?(idx)        -> true or false
+ *
+ *  Returns <code>true</code> if the given index is present in <i>ary</i>.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     h.has_index?(0)    #=> true
+ *     h.has_index?(2)    #=> true
+ *     h.has_index?(3)    #=> false
+ *     h.has_index?(-1)   #=> true
+ *     h.has_index?(-4)   #=> false
+ *
+ */
+
+static VALUE
+rb_ary_has_index(VALUE ary, VALUE pos)
+{
+    VALUE val;
+    long idx;
+
+    idx = NUM2LONG(pos);
+
+    if (idx < 0) {
+       idx += RARRAY_LEN(ary);
+    }
+    if (idx < 0 || RARRAY_LEN(ary) <= idx) {
+       return Qfalse;
+    }
+    return Qtrue;
+}
+
 VALUE
 rb_ary_to_ary(VALUE obj)
 {
@@ -5596,6 +5629,8 @@ Init_Array(void)
     rb_define_method(rb_cArray, "clear", rb_ary_clear, 0);
     rb_define_method(rb_cArray, "fill", rb_ary_fill, -1);
     rb_define_method(rb_cArray, "include?", rb_ary_includes, 1);
+    rb_define_method(rb_cArray, "has_index?", rb_ary_has_index, 1);
+    rb_define_method(rb_cArray, "index?", rb_ary_has_index, 1);
     rb_define_method(rb_cArray, "<=>", rb_ary_cmp, 1);
 
     rb_define_method(rb_cArray, "slice", rb_ary_aref, -1);
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index b4f35af..98a0183 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -932,6 +932,16 @@ class TestArray < Test::Unit::TestCase
     assert_equal(1, a.index(99) {|x| x == 'cat' })
   end
 
+  def test_has_index
+    a = @cls[ 'cat', 99, /a/, 99, @cls[ 1, 2, 3] ]
+    assert(  a.has_index?(0))
+    assert(  a.has_index?(4))
+    assert(! a.has_index?(5))
+    assert(  a.has_index?(-1))
+    assert(  a.has_index?(-5))
+    assert(! a.has_index?(-6))
+  end
+
   def test_values_at
     a = @cls[*('a'..'j').to_a]
     assert_equal(@cls['a', 'c', 'e'], a.values_at(0, 2, 4))