enumerate.cr

class Object
  macro enumerated(method)
    {{method}}

    def {{method.name}}({{*method.args}})
      Enumerator(typeof({{method.name}}({{*method.args.map &.name}}) { |_z| _z })).new do |y|
        {{method.name}}({{*method.args.map &.name}}) do |value|
          y << value
        end
      end
    end
  end
end

class Enumerator(T)
  include Enumerable(T)

  struct Yielder(T)
    def initialize
      @channel = Channel(T).new(20)
    end

    def <<(value : T)
      @channel.send value
    end

    def receive
      @channel.receive
    end
  end

  def initialize(&block : Yielder(T) ->)
    @yielder = Yielder(T).new
    spawn do
      block.call(@yielder)
    end
  end

  def next
    @yielder.receive
  end

  def each
    loop do
      yield self.next
    end
  end
end

class MyClass
  enumerated def each(z)
    yield 1 + z
    yield 2 + z
    yield 3 + z
  end
end

v = MyClass.new.each(10)
p v.next
p v.next
p v.next