README.md in rubype-0.2.1 vs README.md in rubype-0.2.2

@@ -1,62 +1,34 @@
 # Ruby + Type = Rubype
 
 ```rb
+# Assert class of both args is Numeric and class of return is String
 def sum(x, y)
-  x + y
+  (x + y).to_s
 end
-typesig sum: [Numeric, Numeric => Numeric]
-```
+typesig sum: [Numeric, Numeric => String]
 
-This gem brings you advantage of type without changing existing code's behavior.
-
-Matz has mentioned Ruby3.0 with static type at some confluences. But almost all rubyists(include me) are not sure how typed Ruby is.
-
-But it's worth thinking more. This gem is kind of trial without so much side-effect.
-
-# Feature
-### Typed method can coexist with non-typed method
-
-```ruby
-# It's totally OK!!
-class MyClass
-  def method_with_type(x, y)
-    x + y
-  end
-  typesig sum: [Numeric, Numeric => Numeric]
-
-  def method_without_type(x, y)
-    'string'
-  end
+# Assert first arg has method #to_i
+def sum(x, y)
+  x.to_i + y
 end
+typesig sum: [:to_i, Numeric => Numeric]
 ```
 
-### Duck typing
 
-```ruby
+This gem brings you advantage of type without changing existing code's behavior.
 
-class MyClass
-  def foo(any_obj)
-    1
-  end
-  typesig sum: [Any => Numeric]
-end
+# Feature
 
-# It's totally OK!!
-MyClass.new.foo(1)
-# It's totally OK!!
-MyClass.new.foo('str')
-```
-
 ### Advantage of type
 * Meaningful error
 * Executable documentation
 
 ```rb
 require 'rubype'
 
-# ex1
+# ex1: Assert class of args and return
 class MyClass
   def sum(x, y)
     x + y
   end
   typesig sum: [Numeric, Numeric => Numeric]
@@ -69,33 +41,91 @@
 
 MyClass.new.sum(1, 2)
 #=> 3
 
 MyClass.new.sum(1, 'string')
-#=> ArgumentError: Wrong type of argument, type of "str" should be Numeric
+#=> Rubype::ArgumentTypeError: Expected MyClass#sum's 2th argument to be Numeric but got "string" instead
 
 MyClass.new.wrong_sum(1, 2)
-#=> TypeError: Expected wrong_sum to return Numeric but got "str" instead
+#=> Rubype::ReturnTypeError: Expected MyClass#wrong_sum to return Numeric but got "string" instead
 
 
-# ex2
+# ex2: Assert object has specified method
+class MyClass
+  def sum(x, y)
+    x.to_i + y
+  end
+  typesig sum: [:to_i, Numeric => Numeric]
+end
+
+MyClass.new.sum('1', 2)
+#=> 3
+
+MyClass.new.sum(:has_no_to_i, 2)
+#=> Rubype::ArgumentTypeError: Expected MyClass#sum's 1th argument to have method #to_i but got :has_no_to_i instead
+
+
+# ex3: You can use Any class, if you want
 class People
-  type People >= Any, def marry(people)
+  def marry(people)
     # Your Ruby code as usual
   end
+  typesig marry: [People => Any]
 end
-typesig marry: [People => Any]
 
 People.new.marry(People.new)
 #=> no error
 
 People.new.marry('non people')
-#=> ArgumentError: Wrong type of argument, type of "non people" should be People
+#=> Rubype::ArgumentTypeError: Expected People#marry's 1th argument to be People but got "non people" instead
+
 ```
 
+### Typed method can coexist with non-typed method
 
+```ruby
+# It's totally OK!!
+class MyClass
+  def method_with_type(x, y)
+    x + y
+  end
+  typesig sum: [Numeric, Numeric => Numeric]
 
+  def method_without_type(x, y)
+    'string'
+  end
+end
+```
+
+### Duck typing
+You can use `Any` class.
+```ruby
+class MyClass
+  def foo(any_obj)
+    1
+  end
+  typesig foo: [Any => Numeric]
+
+  def sum(x, y)
+    x.to_i + y
+  end
+  typesig sum: [:to_i, Numeric => Numeric]
+end
+
+# It's totally OK!!
+MyClass.new.foo(1)
+# It's totally OK!!
+MyClass.new.foo(:sym)
+
+
+# It's totally OK!!
+MyClass.new.sum(1, 2)
+# It's totally OK!!
+MyClass.new.sum('1', 2)
+```
+
+
 ## Installation
 
 gem install rubype or add gem 'rubype' to your Gemfile.
 
 This gem requires Ruby 2.0.0+.
@@ -114,10 +144,9 @@
 
     > 5 runs, 39 assertions, 0 failures, 0 errors, 0 skips
 
 Push to the branch (`git push origin my-new-feature`)
 
-Create a new Pull Request
+Create a new Pull Request to `develop` branch
 
 ## Credits
 [@chancancode](https://github.com/chancancode) and [This article](http://blog.codeclimate.com/blog/2014/05/06/gradual-type-checking-for-ruby/) first brought this to my attention. I've stolen some idea from them.
-