gistfile1.rbx

class Distance

  FACTORS = {
    :kilometers => 1000.0,
    :meters => 1.0,
    :decimeters => 0.1,
    :centimeters => 0.01,
    :millimeters => 0.001,
  }
  
  UNITS = FACTORS.keys
  
  ### class methods for converting
  def self.convert(value, from_unit, to_unit = :meters)
    value * FACTORS[unit] / FACTORS[otherunit]
  end
  
  class << self
    # convert everything
    UNITS.each do |to_unit|
      UNITS.each do |from_unit|
        define_method "#{from_unit}_to_#{to_unit}" do |value|
          convert(value, from_unit, to_unit)
        end
      end
    end
  end

end