math.huge is a constant. It represents +infinity. 
> = math.huge
inf
> = math.huge / 2
inf
> = -math.huge
-inf
> = math.huge/math.huge   -- indeterminate
nan
> = math.huge * 0         -- indeterminate
nan
> = 1/0
inf
> = (math.huge == math.huge)
true
> = (1/0 == math.huge)
true
Note that some operations on math.huge return a special "not-a-number" value that displays as nan. This is a bit of a misnomer. nan is a number type, though it's different from other numbers:> = type(math.huge * 0)
number 

if tostring(math.abs(a)) == "1.#INF" then print("Неожиданный результат") end

infinity = 1/0 
if a == infinity or a == -infinity then print("Неожиданный результат") end

if c ~= 0 then
  a = b / c
  print(a)
else print("Что я делаю?! Нельзя на ноль делить!") end