vagrant [vagrant]> irb
2.3.0 :001 > def say_hi
2.3.0 :002?>   "Hi, #{name}"
2.3.0 :003?>   end
 => :say_hi
2.3.0 :004 > say_hi(vanessa)
NameError: undefined local variable or method `vanessa' for main:Object
	from (irb):4
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :005 > say_hi("vanessa")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):1:in `say_hi'
	from (irb):5
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :006 > say_hi("vanessa")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):1:in `say_hi'
	from (irb):6
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :007 > say_hi ("vanessa")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):1:in `say_hi'
	from (irb):7
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :008 > say_hi("vanessa")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):1:in `say_hi'
	from (irb):8
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :009 > say_hi
NameError: undefined local variable or method `name' for main:Object
	from (irb):2:in `say_hi'
	from (irb):9
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :010 > def say_hi
2.3.0 :011?>   "Hi, #{name}"
2.3.0 :012?>   end
 => :say_hi
2.3.0 :013 > say_hi("ness")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):10:in `say_hi'
	from (irb):13
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :014 > say_hi(nes)
NameError: undefined local variable or method `nes' for main:Object
	from (irb):14
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :015 > def say_hi
2.3.0 :016?>   "Hi, #{Josh}"
2.3.0 :017?>   end
 => :say_hi
2.3.0 :018 > say_hi("Josh")
ArgumentError: wrong number of arguments (given 1, expected 0)
	from (irb):15:in `say_hi'
	from (irb):18
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :019 > def say_hi(Josh)
2.3.0 :020?>   say_hi("Josh")
2.3.0 :021?>   end
SyntaxError: (irb):19: formal argument cannot be a constant
def say_hi(Josh)
               ^
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :022 > def say_hi(Josh)
2.3.0 :023?>   "Hi, #{Josh}"
2.3.0 :024?>   end
SyntaxError: (irb):22: formal argument cannot be a constant
def say_hi(Josh)
               ^
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :025 > def say_hi(name)
2.3.0 :026?>   "Hi, #{name}"
2.3.0 :027?>   end
 => :say_hi
2.3.0 :028 > say_hi("Josh")
 => "Hi, Josh"
2.3.0 :029 > myarray = [1,2,3,4]
 => [1, 2, 3, 4]
2.3.0 :030 > myarray.sort
 => [1, 2, 3, 4]
2.3.0 :031 > myarray =[ 5,6,1,2]
 => [5, 6, 1, 2]
2.3.0 :032 > myarray.sort
 => [1, 2, 5, 6]
2.3.0 :033 > myarray
 => [5, 6, 1, 2]
2.3.0 :034 > myarray.sort!
 => [1, 2, 5, 6]
2.3.0 :035 > myarray
 => [1, 2, 5, 6]
2.3.0 :036 > anarray = ["ness", "darren", "family", "brunei"]
 => ["ness", "darren", "family", "brunei"]
2.3.0 :037 > an_array.each { |word| puts word}
NameError: undefined local variable or method `an_array' for main:Object
Did you mean?  anarray
	from (irb):37
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :038 > anarray.each { |word| puts word}
ness
darren
family
brunei
 => ["ness", "darren", "family", "brunei"]
2.3.0 :039 > Math.sqrt(1268)
 => 35.608987629529715
2.3.0 :040 > Math.sqrt(1282)
 => 35.805027579936315
2.3.0 :041 > Time.now
 => 2016-05-24 19:10:51 +0000
2.3.0 :042 > time.now
NameError: undefined local variable or method `time' for main:Object
	from (irb):42
	from /usr/local/rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :043 > Array.new(100, "bee")
 => ["bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee", "bee"]
2.3.0 :044 > include Math
 => Object
2.3.0 :045 > sqrt 64
 => 8.0
2.3.0 :046 >