test.lua

function print_r ( t )
    local print_r_cache={}
    local function sub_print_r(t,indent)
        if (print_r_cache[tostring(t)]) then
            print(indent.."*"..tostring(t))
        else
            print_r_cache[tostring(t)]=true
            if (type(t)=="table") then
                for pos,val in pairs(t) do
                    if (type(val)=="table") then
                        print(indent.."["..pos.."] => "..tostring(t).." {")
                        sub_print_r(val,indent..string.rep(" ",string.len(pos)+8))
                        print(indent..string.rep(" ",string.len(pos)+6).."}")
                    else
                        print(indent.."["..pos.."] => "..tostring(val))
                    end
                end
            else
                print(indent..tostring(t))
            end
        end
    end
    sub_print_r(t,"  ")
end

-- Locals
local cos = math.cos
local sin = math.sin
local pi = math.pi
local sqrt = math.sqrt
local min = math.min
local asin = math.asin
local abs = math.abs

-- Calculate distance
 function distance(from, to)
  local distance = 0
  local radius = 6367000
  local radian = pi / 180
  local deltaLatitude = sin(radian * (from.latitude - to.latitude) /2)
  local deltaLongitude = sin(radian * (from.longitude - to.longitude) / 2)

  local circleDistance = 2 * asin(min(1, sqrt(deltaLatitude * deltaLatitude +
     cos(radian * from.latitude) * cos(radian * to.latitude) * deltaLongitude * deltaLongitude)))
  distance = abs(radius * circleDistance)
  return distance
 end

 -- Markers
local markers = {
    { title='Nova Scotia', latitude = -62.937013, longitude = 45.367584}, --  will become position 3
	{ title='Brooklyn', latitude = -73.949204, longitude = 40.644178}, -- will become position 1
	{ title='South Philadelphia West', latitude = -75.181275, longitude = 39.918163} -- will become position 2
}

-- Center; could be your current GPS location
centerPoint = {latitude = -73.995895, longitude = 40.718119} -- new york

-- Set distances in markers
for i, Prop in ipairs(markers) do
	Prop['distance'] = distance(centerPoint, markers[i])
end

-- Sort by distance
function compare(a,b)
  return a['distance'] < b['distance']
end
table.sort(markers, compare)

-- Print sorted markers
print_r(markers)