wombat.rb

require 'forwardable'

class Wombat
  NO_DEFAULT = Object.new
  
  include Comparable
  include Enumerable
  extend Forwardable

  def_delegators :@list, :[], :[]=, :fetch, :<<, :delete, :size, :<=>

  def initialize(size, default = NO_DEFAULT, &block)
    @list = parse_args(size:, default:, &block)
  end

  def inspect = @list

  def each(&block)
    return enum_for(__method__) unless block_given?

    @list.each { block.call(_1) }
  end

  private

  def parse_args(size:, default:, &block)
    if default == NO_DEFAULT
      return Array.new(size) unless block_given?
    else
      return Array.new(size, default) unless block_given?

      warn 'warning: block supersedes default value argument'
    end

    Array.new(size) { |index| block.call(index) }
  end
end