Torino scale in lua

torino.lua

local math = require('math')

local torino = {}

torino.colors = {
   [0] = nil,
   [1] = "green",
   [2] = "yellow",
   [3] = "yellow",
   [4] = "yellow",
   [5] = "orange",
   [6] = "orange",
   [7] = "orange",
   [8] = "red",
   [9] = "red",
   [10] = "red"
}

local log10 = function (x) return math.log(x, 10) end

function torino.compute(energy, probability)
   if (((log10(energy) + 1) / 3  + (log10(probability) + 2) / 2) < 0)
         or (log10(energy) < 0) then
         return 0, torino.colors[0]
   elseif (((log10(energy) + 1) / 3) + ((log10(probability) + 2) / 2) >= 0)
            and (log10(energy) >= 0)
            and (((log10(energy) - 2) / 3) + ((log10(probability) + 2) / 2) < 0)
            and (log10(probability) < -2) then
         return 1, torino.colors[1]
   elseif (((log10(energy) - 2) / 3) + ((log10(probability) + 2) / 2) >= 0)
            and ((((log10(energy) - 5) / 3) + ((log10(probability) + 2) / 2)) < 0) then
         return 2, torino.colors[2]
   elseif ((log10(probability) >= -2)
            and (log10(energy) >= 0)
            and (probability < 0.99)
            and (log10(energy) < 2)) then
         return 3, torino.colors[3]
   elseif ((log10(probability) >= -2)
            and (log10(energy) >= 2)
            and (((log10(energy - 5) / 3) + (log10(probability + 2) / 2)) < 0))
            and (probability < 0.99) then
         return 4, torino.colors[4]
   elseif (((log10(energy - 5) / 3) + (log10(probability + 2) / 2)) >= 0)
            and (probability < 0.99)
            and (log10(energy) < 5) then
         return 5, torino.colors[5]
   elseif ((log10(energy - 5) / 3) + (log10(probability + 2) / 2) >= 0)
            and (log10(probability) < -2) then
         return 6, torino.colors[6]
   elseif (log10(probability) >= -2)
           and (log10(energy) >= 5)
           and (probability < 0.99) then
         return 7, torino.colors[7]
   elseif (probability > 0.99)
            and (log10(energy) >= 0)
            and (log10(energy) < 2) then
         return 8, torino.colors[8]
   elseif (probability > 0.99)
            and (log10(energy) >= 2)
            and (log10(energy) < 5) then
         return 9, torino.colors[9]
   elseif (probability > 0.99) and (log10(energy) >= 5) then
         return 10, torino.colors[10]
   end
   -- ideally unreachable
   return nil, nil
end

return torino