Operator precedence

   +-----+-------------------------------------------------+
   |  1. | ! ~@ +@                                         |
   |  2. | **                                              |
   |  3. | -@                                              |
   |  4. | * / %                                           |
   |  5. | + -                                             |
   |  6. | << >>                                           |
   |  7. | &                                               |
   |  8. | | ^                                             |
   |  9. | > >= < <=                                       |
   | 10. | <=> == === != =~ !~                             |
   | 11. | &&                                              |
   | 12. | ||                                              |
   | 13. | .. ...                                          |
   | 14. | ? :                                             |
   | 15. | rescue                                          |
   | 16. | = **= *= /= %= += -= <<= >>= &= |= ^= &&= ||=   |
   | 17. | defined?                                        |
   | 18. | not                                             |
   | 19. | or and                                          |
   | 20. | if unless while until                           |
   | 21. | { } do end                                      |
   +-----+-------------------------------------------------+

# Defining an unary operator
class String
  def +@
    "positive #{self}"
  end
end

+"number"
=> "positive number"

# #super and #superclass

# Defining a binary operator
class String
  def -(trash)
    self.gsub(/#{trash}/, '')
  end
end

"abcdef" - "cde"
=> "abf"

class Monster
  def react(action)
    :roar
  end
end

class Komoju < Monster
  def react(action)
    if action == :pat
      return :purr
    end
    super
  end
end

# Get characters of string
'abc'.chars
=> ["a", "b", "c"]

# Get character codes of string
'abc'.chars.map(&:ord)
=> [97, 98, 99]

Komoju.new.react(:pat)
=> :purr

Komoju.new.react(:poke)
=> :roar

Komoju.superclass
=> Monster


# Modules
module LaserWeapon
  def shoot_laser
    'Pew pew pew!'
  end
end

class Komoju
  include LaserWeapon
end

Komoju.new.shoot_laser
=> 'Pew pew pew!'