haskelldistance.hs

import Data.Geo.Radians
import Time
 
radius = 6371
 
distance :: Double -> Double -> Double -> Double -> Double
distance latA lngA latB lngB = result 
    where 
      latAr = toRadians latA
      lngAr = toRadians lngA
      latBr = toRadians latB
      lngBr = toRadians lngB
 
      deltaLat = latBr - latAr
      deltaLng = lngBr - lngAr
      result = radius * 2 * (asin (sqrt (sin $ deltaLat/2.0) ** 2.0 + (cos latAr) * 
                                   (cos latBr) * 
                                   (sin $ (deltaLng / 2.0) ** 2.0)))
 
main = do
  let rangeLat = [-90, -87.5 .. 90]
  let rangeLng = [-180, -177.5  .. 180]
  let result = [distance j k l m | j <- rangeLat, k <- rangeLng, l <- rangeLat, m <- rangeLng]
  print $ take 4 result -- just to make sure it's doing something.
  print $ last result