From: ahoward <ahoward@...>
Date: 2003-03-22T03:44:31+09:00
Subject: Re: infinite Time

On Sat, 22 Mar 2003 nobu.nokada@softhome.net wrote:

> class Time
>   NEGATIVE_INFINITY = -1.0 / 0
>   INFINITY = 1.0 / 0
>   EPOCH = 0
> end

looks promising.  however, can anyone explain why this approach to
implementing the comparisions does not work?????

  class Time
    INF   = INFINITY          =  1.0 / 0
    NINF  = NEGATIVE_INFINITY = -1.0 / 0
    EPOCH = Time.at(0)

    class << INFINITY
      include Comparable
      def <=> o;self.id == o.id ? 0 : 1;end
    end

    class << NEGATIVE_INFINITY
      include Comparable
      def <=> o;self.id == o.id ? 0 : -1;end
    end
  end

  def display command
    puts "#{command}"
    puts "\t# >> #{eval command}"
  end


  display %Q(Time::INF  <=> Time::NINF)
  display %Q(Time::NINF <=> Time::INF)

  display %Q(Time.now <=> Time::INF)
  display %Q(Time::INF <=> Time.now)

  display %Q(Time.now <=> Time::NINF)
  display %Q(Time::NINF <=> Time.now)

# why does this raise an exception??
  display %Q(Time::INF > Time.now)


i could use singleton objects for INF and NINF, but would like to avoid that.

i am unclear as to why

  class << object
    include Comparable
    def <=> ...
  end

does NOT, in this case, seem to redefine the '>' operator.

i swear, every time i think i understand this bloody 'class << self'
business...

i *thought* the above would (re)define all the comparison operators for the
singleton class of INF...


-a

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  | Ara Howard
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