module Geocoder::Calculations

def distance_between(point1, point2, options = {}, *args)


* :units - :mi (default) or :km

The options hash supports:

which returns a [lat,lon] array
* a geocoded object (one which implements a +to_coordinates+ method
* a geocodable address (string)
* an array of coordinates ([lat,lon])

Geocoder methods that accept points as arguments. They can be:
The points are given in the same way that points are given to all
Takes two points and an options hash.
Distance between two points on Earth (Haversine formula).
# 
def distance_between(point1, point2, options = {}, *args)
  if args.size > 0
    warn "DEPRECATION WARNING: Instead of passing lat1/lon1/lat2/lon2 as separate arguments to the distance_between method, please pass two two-element arrays: [#{point1},#{point2}], [#{options}, #{args.first}]. The old argument format will not be supported in Geocoder v.1.0."
    point1 = [point1, point2]
    point2 = [options, args.shift]
    options = args.shift || {}
  end
  # set default options
  options[:units] ||= :mi
  # convert to coordinate arrays
  point1 = extract_coordinates(point1)
  point2 = extract_coordinates(point2)
  # convert degrees to radians
  point1 = to_radians(point1)
  point2 = to_radians(point2)
  # compute deltas
  dlat = point2[0] - point1[0]
  dlon = point2[1] - point1[1]
  a = (Math.sin(dlat / 2))**2 + Math.cos(point1[0]) *
      (Math.sin(dlon / 2))**2 * Math.cos(point2[0])
  c = 2 * Math.atan2( Math.sqrt(a), Math.sqrt(1-a))
  c * earth_radius(options[:units])
end