defaults

# Default methods: a trait can carry bodies of its own.

trait Greet
  abstract def name : String

  # Not abstract: every implementer gets this one for free, written in
  # terms of the requirement.
  def greeting : String
    "Merhaba, #{name}!"
  end

  def shout : String
    greeting.upcase
  end
end

struct Person
  def initialize(@name : String)
  end
end

impl Greet for Person
  def name : String
    @name
  end
end

struct Robot
  def initialize(@id : Int32)
  end
end

impl Greet for Robot
  def name : String
    "unit #{@id}"
  end

  # An implementer may replace a default.
  def greeting : String
    "BEEP #{name}"
  end
end

puts Person.new("Ada").greeting
puts Person.new("Ada").shout
puts Robot.new(7).greeting
puts Robot.new(7).shout