haversine.lua

require “math”
function haversine(lat1, lon1, lat2, lon2)
    lat1 = lat1 * math.pi / 180
    lon1 = lon1 * math.pi / 180
    lat2 = lat2 * math.pi / 180
    lon2 = lon2 * math.pi / 180
    
    lat_dist = lat2-lat1
    lon_dist = lon2-lon1
    lat_hsin = math.pow(math.sin(lat_dist/2),2)
    lon_hsin = math.pow(math.sin(lon_dist/2),2)

    a = lat_hsin + math.cos(lat1) * math.cos(lat2) * lon_hsin
    return 2* 6372.8 * math.asin(math.sqrt(a))
end