class Test
    def Test.do(x)
        puts "#{x} was passed as an argumnet!"
    end
end

Test.do(3)

OUTPUT
3 was passed as an argument!

class Person
	def initialize(name, age)
		@name, @age = name, age
	end

	def to_s
		"#@name is #@age"
	end
end

class Student < Person
	def initialize(name, age, average)
		#pass the parameters to the Parent
		super(name, age)
		@average = average
	end

	def to_s
		#call parent version of method first with super()
		super + " and has an average of #@average"
	end
end

per = Person.new("Jesse", 16)
stu = Student.new("Anna Smith", 234, 86)

puts per #calls per.to_s
puts stu

OUTPUT

Jesse is 16
Anna Smith is 234 and has an average of 86

class Integer
    def even?
        (self % 2).zero? #could also be "== 0"
    end
end

OUTPUT with interactive ruby:
$ irb --simple-prompt
>> require 'test' #name of file
=> true
>> 3.even?
=> false
>> 4.even?
=> true
>>

>> raise JesseError = Class.new(ArgumentError), "A JesseError occured!"
JesseError: A JesseError occured!
        from (irb):7
>>

#   Array#collect
[1, 2, 3, 4].collect { |x| x + 2 }
#this means for each element, take it, add 2, and keep the result
#=> [3, 4, 5, 6]

#   String#gsub -- a globab String substitution using regexp
>> "Hello, my name is Jesse.".gsub(/[a-z]{3}/) { |match|  match.upcase }
=> "HELLo, my NAMe is JESSe."

#using yield to create an iterator
def squares_upto(n)
    1.upto(n) { |x| yield x * x }
end

>> squares_upto(10) { |square| puts square }
1
4
9
16
25
36
49
64
81
100
=> 1
>>