A better range generator function at Lua...

range.lua

-- as multi-dispatch pseudo-code
--
-- range(init, final, step):
---- return
---- [ where init > final ]
--
-- range(final):
---- return 0, range(0 + 1, final, 1)
---- [ where final is Positive Integer ]
--
-- range(init, final):
---- return init, range(init + 1, final, 1)
---- [ where both are Positive Integers ]
--
-- range(init, final, step):
---- return init, range(init + step, final, step)
---- [ where all the args are Positive Integers ]
--

function range (i, f, s)
  if not f then
    f = i
    i = 0
  end
  s = s or 1 -- 1 is default step
  if i > f then
    return
  else
    return i, range (i + s, f, s)
  end
end

-- test
print (range (10)) --> from 0 to 10
print (range (15, 25)) --> from 15 to 25
print (range (10, 50, 5)) --> from 10 to 50, jumping over each 5 elements

-- end of script