gistfile1.rb

require 'ostruct'
require 'date'

class OrdersReport < Struct.new(:orders,:date_range)
  def total_sales_within_date_range
    orders.select {|order| date_range.include?(order.placed_at) }
          .map(&:amount)
          .reduce(0.0,:+)
  end
end

class DateRange < Struct.new(:start_date, :end_date)
  def include?(date)
    (start_date..end_date).cover? date
  end
end

class Order < Struct.new(:amount, :placed_at)
end