4 files changed, 39 insertions, 0 deletions
diff --git a/build_config.rb b/build_config.rb
index d41c44b98..baf0a6233 100644
--- a/build_config.rb
+++ b/build_config.rb
@@ -35,6 +35,9 @@ MRuby::Build.new do |conf|
   # Use extensional Array class
   conf.gem "#{root}/mrbgems/mruby-array-ext"
 
+  # Use extensional Hash class
+  conf.gem "#{root}/mrbgems/mruby-hash-ext"
+
   # Generate binaries
   # conf.bins = %w(mrbc mruby mirb)
   
diff --git a/mrbgems/mruby-hash-ext/mrbgem.rake b/mrbgems/mruby-hash-ext/mrbgem.rake
new file mode 100644
index 000000000..3163c8c88
--- /dev/null
+++ b/mrbgems/mruby-hash-ext/mrbgem.rake
@@ -0,0 +1,4 @@
+MRuby::Gem::Specification.new('mruby-hash-ext') do |spec|
+  spec.license = 'MIT'
+  spec.authors = 'mruby developers'
+end
diff --git a/mrbgems/mruby-hash-ext/mrblib/hash.rb b/mrbgems/mruby-hash-ext/mrblib/hash.rb
new file mode 100644
index 000000000..3e1bac0a2
--- /dev/null
+++ b/mrbgems/mruby-hash-ext/mrblib/hash.rb
@@ -0,0 +1,12 @@
+class Hash
+  def merge!(other, &block)
+    if block
+      other.each_key{|k|
+        self[k] = (self.has_key?(k))? block.call(k, self[k], other[k]): other[k]
+      }
+    else
+      other.each_key{|k| self[k] = other[k]}
+    end
+    self
+  end
+end
diff --git a/mrbgems/mruby-hash-ext/test/hash.rb b/mrbgems/mruby-hash-ext/test/hash.rb
new file mode 100644
index 000000000..98eb313a4
--- /dev/null
+++ b/mrbgems/mruby-hash-ext/test/hash.rb
@@ -0,0 +1,20 @@
+##
+# Hash(Ext) Test
+
+assert('Hash#merge!') do
+  a = { 'abc_key' => 'abc_value', 'cba_key' => 'cba_value' }
+  b = { 'cba_key' => 'XXX',  'xyz_key' => 'xyz_value' }
+
+  result_1 = a.merge! b
+  
+  a = { 'abc_key' => 'abc_value', 'cba_key' => 'cba_value' }
+  result_2 = a.merge!(b) do |key, original, new|
+    original
+  end
+
+  result_1 == {'abc_key' => 'abc_value', 'cba_key' => 'XXX',
+               'xyz_key' => 'xyz_value' } and
+  result_2 == {'abc_key' => 'abc_value', 'cba_key' => 'cba_value',
+               'xyz_key' => 'xyz_value' }
+end
+