Calculator

w, h = term.getSize()
term.setBackgroundColor(colors.green)
term.clear()
term.setCursorPos(w/2 - 4, 1)
term.write("Calculator")
term.setCursorPos(1, 2)
term.write("   +  -  *  /  **  ^  %   ")
term.setCursorPos(1, 4)
term.write("Input: ")
term.setCursorPos(8, 4)
local input = read()
local tArgs = {}
local count = 1
for i in string.gmatch(input, "%S+") do
  tArgs[count] = i
  count = count + 1
end
local nums = {}
local operands = {}
local result = nil
for i, v in pairs(tArgs) do
  if tonumber(v) and v ~= "-" then
    nums[i] = tonumber(v)
    operands[i] = false
  else
    nums[i] = false
    operands[i] = v
  end
end

local initial = true
for i = 1, #tArgs do
  if nums[i] == false then
    if initial then
      result = nums[i - 1]
      initial = false
    end
    if operands[i] == "+" then
      result = result + nums[i + 1]
    elseif operands[i] == "-" then
      result = result - nums[i + 1]
    elseif operands[i] == "*" then
      result = result * nums[i + 1]
    elseif operands[i] == "/" then
      result = result / nums[i + 1]
    elseif operands[i] == "**" or operands[i] == "^" then
      result = result ^ nums[i + 1]
    elseif operands[i] == "%" then
      result = result % nums[i + 1]
    else
      print("ERROR: Unsupported operation")
      result = nil
    end
  end
end
print(result)
sleep(2)