A Module is a collection of methods and constants. The methods
in a module may be instance methods or module methods. Instance
methods appear as methods in a class when the module is
included, module methods do not. Conversely, module methods may
be called without creating an encapsulating object, while
instance methods may not. (See Module#module_function) In the
descriptions that follow, the parameter syml refers to a symbol,
which is either a quoted string or a Symbol (such as :name).
module Mod include Math CONST = 1 def meth # ... end end
Mod.class #=> Module Mod.constants #=> ["E", "PI", "CONST"]
Mod.instance_methods #=> ["meth"]