modify

.gitignore

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+pkg/*
+*.gem
+.bundle

Gemfile

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+source :gemcutter
+
+# Specify your gem's dependencies in ruby_extend.gemspec
+gemspec

Rakefile

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+require 'bundler'
+Bundler::GemHelper.install_tasks

lib/ruby_extend.rb

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+require 'ruby_extend/hash_extendsions'
+

lib/ruby_extend/hash_extendsions.rb

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+module RubyExtend
+  module HashExtendsions
+    def self.included(base)
+      base.send :include, InstanceMethods
+    end
+
+    module InstanceMethods
+      def hash_reverse
+        hash_new = {}
+        self.each {|key,value|
+          if not hash_new.has_key?(key) then hash_new[value] = key end
+        }
+        return hash_new
+      end
+    end
+  end
+end
+
+class Hash
+  include RubyExtend::HashExtendsions
+end

lib/ruby_extend/version.rb

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+module RubyExtend
+  VERSION = "0.0.1"
+end

ruby_extend.gemspec

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+# -*- encoding: utf-8 -*-
+require File.expand_path("../lib/ruby_extend/version", __FILE__)
+
+Gem::Specification.new do |s|
+  s.name        = "ruby_extend"
+  s.version     = RubyExtend::VERSION
+  s.platform    = Gem::Platform::RUBY
+  s.authors     = []
+  s.email       = []
+  s.homepage    = "http://rubygems.org/gems/ruby_extend"
+  s.summary     = "TODO: Write a gem summary"
+  s.description = "TODO: Write a gem description"
+
+  s.required_rubygems_version = ">= 1.3.6"
+  s.rubyforge_project         = "ruby_extend"
+
+  s.add_development_dependency "bundler", ">= 1.0.0"
+
+  s.files        = `git ls-files`.split("\n")
+  s.executables  = `git ls-files`.split("\n").map{|f| f =~ /^bin\/(.*)/ ? $1 : nil}.compact
+  s.require_path = 'lib'
+end