Namespaces, Source Files, and Distribution(Chapter 16 of Programming Ruby)

　　Putting code inside a module or class is a good way of separating it from other code.Ruby’s Math module is a good example—it defines constants such as Math::PI and Math::E and methods such as Math.sin and Math.cos. You can access these constants and methods via the Math module object:

　　Math::E # => 2.71828182845905

　　Math.sin(Math::PI/6.0) # => 0.5