mondays.rb

#! ruby19

require 'date'

class EndlessEnum
  include Enumerable

  def initialize(x, method = :succ)
    @x = x
    @method = method
  end

  # They never come back!
  def each
    y = @x

    loop do
      yield y
      y = y.send @method
    end

    self
  end
end

class Weekday
  attr_reader :date

  def initialize(wd, start = Date.today)
    wd = wd.to_s
    @wd = /\?\z/ =~ wd ? wd : "#{wd}?"

    until start.send(@wd)
      start = start.succ
    end

    @date = start
  end

  def succ
    self.class.new(@wd, @date + 1)
  end
end

i = 0
EndlessEnum.new(Weekday.new(:monday)).each do |mon|
  printf "%p  %s monday? %p\n", mon, mon.date, mon.date.monday?

  i += 1
  break if i >= 10
end