dispatch

# A trait is a type: one list, many kinds, one question.

trait Speak
  abstract def sound : String
end

struct Dog
  def initialize(@name : String)
  end

  def name : String
    @name
  end
end

struct Cat
  def initialize(@name : String)
  end

  def name : String
    @name
  end
end

impl Speak for Dog
  def sound : String
    "hav"
  end
end

impl Speak for Cat
  def sound : String
    "miyav"
  end
end

# `of Speak` types the array by the trait, so both fit.
animals = [Dog.new("Karabaş"), Cat.new("Pamuk")] of Speak
animals.each { |animal| puts animal.sound }

# A function can ask for the trait rather than a particular type.
def chorus(voices : Array(Speak)) : String
  voices.map { |v| v.sound }.join(" ")
end

puts chorus(animals)