########Programming Fundamental########
# If it can happen, it will happen.
# Control your flow so crap can't happen. 
class AnythingElse
  # This is a class to represent AnythingElse other than what
  # can_happen will understand
  def initialize
    # Personified by the text 'anything else'  
    @anything_else = 'anything else'
  end
  def to_s
    # Only has one method, a to_s to insure that we return the text 
    # value of the class
    return @anything_else
  end
end 
# if it can happen, it will happen
def can_happen(*anything) 
  # I accept any number of arguments..
  if anything.length >= 1 # If i get one or more arguments
    anything.each do |thing| # For each argument i do the following
      if thing && thing != true 
        # If the argument exists, and it is not true, we cannot understand it
        # Note, false, nil and blank arguments do not fall into this category
        # raise an Exception to cause the process to stop.  
        raise "I don't understand " + thing.to_s
      elsif thing == false
        # If the argument received is false
        puts "If it is #{thing} it Cannot Happen"
      elsif thing == nil
        # If the argument received is nil
        puts "If it is nothing it Cannot Exist."
      else 
        # Otherwise the only option left is that the argument is true
        puts "If it is #{thing} it Will Happen"
      end
    end
  else
    # If no arguments are passed.  
    puts "If it is nothing it Cannot Exist"
  end
end
# Begin to use the method.  Surround with begin/end to insure that you can 
# rescue exceptions  
begin 
  can_happen() # Call can_happen with no arguments
  can_happen(false, nil, true) # Call can_happen with all other valid arguments
  # Call can_happen with several invalid arguments.  
  can_happen(AnythingElse.new, 'crap', 'can\'t happen', 0, 0.0, 'true')
  # Any code that you are testing for exceptions needs to be between 'begin' and 'rescue'
rescue Exception => e # Catch any Exception that occurs
  # Print out Exception and stack trace.  
  puts e.inspect
  print "  "+e.backtrace.join("\n  ")
else 
  # The program completed without any Exceptions
  puts "I fully understand!"
ensure 
  # This will always happen whether there is an error or not.  
  puts "\nYou cannot fool me!"
# end of 'begin' block
end