From: KCons <consalus@...>
Date: 2007-02-23T15:35:06+09:00
Subject: Cute little simple scheduling code hack

I'm sure there is some far superior prior art out there somewhere, but
this is a useful little hack I threw together today that I thought
someone else might find interesting.

I wanted to do a little task every few seconds for some duration of
time, and after a bit of overkill I came up with a little library that
lets me do stuff like:

every( 5.seconds ).for( 2.days ) { puts "Chunky bacon, k?" }

or

every( 2.minutes ).until ( Time.now + 4.hours ) { dance_for_a_while }

or even

class String
  def gradual_out( n = 1 )
   ix = 0
   every( n.seconds ).unless(lambda {ix >= size}) do
     print self[ix].chr
     ix += 1
   end
  end
end

"Tuesday is the new Thursday".gradual_out( 400.milliseconds )


Fun to play with.
Again, just a quick hack, so if you see any glaring issues or useful
improvements, let me know, because I'm sure I'll find use for it again
later.

--Code below--

class Scheduler
  def initialize( int )
    @interval = int
  end

  def for( secs )
    self.until( Time.now + secs ) { |x| yield x }
  end

  def until( endtime )
    self.unless( lambda { Time.now >= endtime } ) { |x| yield x }
  end

  def unless( cond )
    while !cond.call do
      current = Time.now
      yield current
      wait_time = (current + @interval) - Time.now
      begin
        sleep( wait_time ) unless wait_time <= 0 or cond.call
      rescue Interrupt
        break
      end
    end
  end
end

module Kernel
  def every( int )
    Scheduler.new( int )
  end
end

class Numeric
  def seconds; self; end
  def minutes; self * 60; end
  def hours; self.minutes * 60; end
  def milliseconds; self / 1000.0; end
  def days; self.hours * 24; end
end