nil is false, anything else is true.
false is false

0 is not false
---
http://www.ruby-doc.org

% ri ClassName  (Ruby Doc)
% ri method

Everything is an object:

number=Math.abs(number) // Java
number = number.abs # Ruby

Character indentation preferred with two spaces vs tabs

def say_goodnight(name)
  result = "Good night, #{name.capitalize}"
  return result
end

$global   - Global variables
@instance - instance variable
@@class   - class variables

* Local Variables, Method Parameters, and Method names must start with Uppercase
* Constants are CONSTANTS - note that they hold a reference to an object
* No semicolons at end of statement


* Arrays

	a = [1, 'cat', 3.14]
	a[2] = nil; # Nil is Ruby's NULL 
	a = %w{ ant bee cat dog elk } # array shortcut

* Hashes
	inst_hash = {
		'red'	=> "envelope",
		'green' => "money",
	}
	
	inst_has['red'] ---> "envelope"

* Control Structures (if)

	if count > 10
	  puts "Try again"
	elsif tries == 3
	  puts "You lose"
	else 
	  puts "Enter a number"
	end

	puts "Danger, dude" if aliens > 500

(No braces, end is terminator)

* Control Structures (for)
	for ... in ... [do | : ]
		...
	end

* Control Structures (while)

	while line = gets
	  puts line.downcase
	end

	square = 2
	square = square*square while square < 1000

* Control Structures (case)
	case
		when ...

		when ...
	else
		...
	end

* Code Blocks and Callbacks

	{ puts "Whatever" }
	do
	  club.enroll(person)
	  person.add
	end

	{} braces bind more tightly then do .. end

* Iterators

	animals = %w (ant bee cat dog elk ) 
	animals.each {|animal| puts animal }

	['cat', 'dog', 'horse' ].each {|name| print name, " " }

* Class

	class Song
	  def initialize(name, artist, duration)
	    @name		= name
		@artist		= artist
		@duration 	= duration
 	  end # end initialize
	end  # end class

* Builtin functions
	song.inspect (dump)
	song.to_s (serialize to string)

-----------------------------------------------------------------------------------
Variables

* All variables are references to an object.

	person1="Tim"
	person2=person1
	person1[0] = 'K'

	person1 -> "Kim"
	person2 -> "Kim"

* So you can prevent objects from being changed by freeze

	person1="Tim"
	person2=person1
	person1.freeze
	person1[0] = 'K'

	person1 -> "Jim"
	person2 -> "Kim"
-----------------------------------------------------------------------------------
Classes

* Single Inheritance and Parents (note Mixins differentiator)

	class KaraokeSong < Song
		def initialize(name,artist,duration,lyrics)
			super (name, artist, duration)
			@lyrics = lyrics
		end # initialize

		def to_s
			super + " [#@lyrics]"
		end #to_s

	end # class

* Class Methods are not tied to specific object - def ClassName.method_name

	class MyLogger
		private_class_method :new
		@@logger = nil

		def MyLogger.create
			@@logger = new unless @@logger
			@@logger
		end
	end

* Public, Private, Protected

	class MyClass

		def method_public
		end

		protected

		def method_protected
		end

		private
		def method_private
		end
	end

	class MyClass
		def method1
		end

		public: method1, :method4
		protected: method5
		private:method6
	end

* Scope ::

	OUTER_CONST = 99
	class Const
	
		def get_const
			CONST
		end

		CONST=OUTER_CONST+1
	end

	Const.new.get_const -> 100
	Const::CONST		-> 100
	::OUTER_CONST		-> 99

* Yield

	class Creator
	
		def create_block
			puts "123"
			puts yield
		end
	end
	block = Creator.new.create_block {"original"}

Outputs:
123
original

-----------------------------------------------------------------------------------
Modules

* Defines a namespace

	module Trig
		PI = xxx
	
		def Trig.sin(x)

		end
	end #module

* Now you can really screw up stuff with mixins

	module DebugModule
		def what_the_fuck

		end
	end

	class OneClass
		include Debug

	end

	class SecondClass

	end

	one = OneClass.new()
	two = SecondClass.new()
	one.what_the_fuck()
	two.what_the_fuck()