Distance between 2 addresses in CoffeeScript

A small script to find the distance of two addresses using the Google Maps API:

	#! /usr/bin/env coffee
	Http = require 'http'
	Number::toRad = -> this * (Math.PI / 180)
	# http://www.movable-type.co.uk/scripts/latlong.html
	haversine = (p, q) ->
	R = 6371
	latDist = (q.lat - p.lat).toRad()
	lngDist = (q.lng - p.lng).toRad()
	qLat = q.lat.toRad()
	pLat = p.lat.toRad()
	a = Math.sin(latDist/2) * Math.sin(latDist/2) +
	Math.sin(lngDist/2) * Math.sin(lngDist/2) * Math.cos(qLat) * Math.cos(pLat)
	c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a))
	d = R * c
	d / 1.6 # convert to miles
	getLatLng = (address, onOK, onErr) ->
	opts =
	host: "maps.googleapis.com",
	port: 80,
	path: "/maps/api/geocode/json?address=#{address}&sensor=false"
	Http.get opts, (res) ->
	res.setEncoding 'utf8'
	data = []
	res.on 'data', (chunk) ->
	data.push chunk
	res.on 'end', () ->
	j = JSON.parse(data.join "")
	if j.status is "OK"
	loc = j.results[0].geometry.location
	onOK({lat: loc.lat, lng: loc.lng})
	else
	onErr("Error #{j.status}")
	.on 'error', (e) -> onErr("Error #{e.message}")
	distance = (address1, address2) ->
	err = (msg) ->
	console.log "Error: #{msg}"
	console.exit 1
	compute = (p, q) ->
	dist = haversine(p, q).toFixed(3)
	[a1, a2] = [unescape(address1), unescape(address2)]
	console.log "Distance between #{a1} & #{a2}: #{dist} miles"
	get2 = (p) -> getLatLng(address2, ((q) -> compute(p, q)), err)
	getLatLng(address1, get2, err)
	address1 = escape(process.argv[2])
	address2 = escape(process.argv[3])
	distance address1, address2

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