root/lang/ruby/date_time-duration/lib/date_time/duration.rb @ 3656

require 'date'
# SYNOPSYS
#   dt = DateTime.new(2007, 12, 25)
#   birth = DateTime.new(1984, 12, 26)
#   dur = DaTeTime::Duration.new(birth, dt)
#   dur.years.to_i  # => 22
class DateTime::Duration
  def initialize from, to
    @flag = ( from <= to ) ? 1 : -1
    @from, @to = ( from <= to ) ? [from, to] : [ to, from ]
    @duration = to.ajd - from.ajd
  end

  # It doesn't care about leap seconds.
  def seconds
    @duration * 24 * 60 * 60 
  end

  def minutes
    @duration * 24 * 60
  end

  def hours
    @duration * 24
  end

  def days
    @duration
  end

  def weeks
    @duration / 7
  end

  # This method return not Rational but Fixnum.
  def months
    if @months.nil?
      i = 0
      while ( ( @from >> i ) <= @to ) do
        i += 1
      end

      @months = ( @flag * ( i - 1 ) )
    end
    
    return @months
  end

  def years
    months / 12
  end
end