CalcPlus v1.1 Lite

-- CalcPlus v1.1 Lite | Last Updated 10/26/2013
-- Minimal Requirement: Normal Computer
-- Written by DiabolusNeil

os.pullEvent = os.pullEventRaw

local num1, num2, func, answer, fault, run
local empty = ""
local version = "v1.1"

local function main()
  term.clear()
  term.setCursorPos(17,1)
  print("CalcPlus "..version.." Lite")
  term.setCursorPos(18,2)
  print("By DiabolusNeil\n")
  print("First number:")
  print("Function:")
  print("Second number:")
  if answer ~= nil then
    term.setCursorPos(1,18)
    print("Last Answer: "..answer)
  end
  term.setCursorPos(15,4)
  num1 = read()
  term.setCursorPos(11,5)
  func = read()
  term.setCursorPos(16,6)
  num2 = read()
  print("")

  if num1 == "ans" then num1 = answer end
  if num2 == "ans" then num2 = answer end

  if func == "+" then
    answer = num1 + num2
  elseif func == "-" then
    answer = num1 - num2
  elseif func == "*" then
    answer = num1 * num2
  elseif func == "/" then
    answer = num1 / num2
  elseif func == "^" then
    answer = num1 ^ num2
  elseif func == empty or num1 == empty or num2 == empty then
    fault = "Missing information"
  elseif type(num1) or type(num2) == string then
    fault = "Invalid given information"
  else
    fault = "Invalid given information"
  end

  if fault == nil then
    print(num1.." "..func.." "..num2.." = "..answer)
  else
    print("ERROR: "..fault)
  end

  print("")
  sleep(0.5)
  print("Do you want to make a new calculation?")
  print("ENTER = Yes | Anything Else = No")
  event, key = os.pullEvent("key")

  if key == 28 then
    run = true
  else
    run = false
  end
end

-- Actual program
run = true
while run do
  fault = nil
  main()
end
term.clear()
term.setCursorPos(1,1)