CC Redstone XOR Gate

local tArgs = {...}

if #tArgs ~= 1 then
   print("Usage: xorGate <sides>")
   print("  -- the left of the screen is A, the screen is B")
   print("  -- the right of the screen is C, the back is output")
   print("  -- if sides is 1, the system will check A and B")
   print("  -- if sides is 2, the system will check B and C")
   print("  -- if sides is 3, the system will check A and C")
   print("  -- if sides is 4, the system will check A, B, and C")
   print("  -- all inputs must be true(active) for the output to be true")
   return
end

local function testSide(side)
   return ( (redstone.getInput(side)) or (redstone.getBundledInput(side) >0) )

end

local sides = tonumber(tArgs[1])

if sides < 1 then
  sides = 1
elseif sides > 4 then
  sides = 4
end

while true do

   if ( sides == 1 ) then
     if ( (testSide("left") and not testSide("front")) or (not testSide("left") and testSide("front")) ) then
       redstone.setOutput("back",true)
       redstone.setBundledOutput("back",255)
     end
   elseif ( sides == 2 ) then
     if ( (testSide("right") and not testSide("front")) or (not testSide("right") and testSide("front")) ) then
       redstone.setOutput("back",true)
       redstone.setBundledOutput("back",255)
     end
   elseif ( sides == 3 ) then
     if ( (testSide("right") and not testSide("left")) or (not testSide("right") and testSide("left")) ) then
       redstone.setOutput("back",true)
       redstone.setBundledOutput("back",255)
     end
   elseif ( sides == 4 ) then
     if ( (testSide("right") and not testSide("front") and not testSide("left")) or
          (not testSide("right") and testSide("front") and not testSide("left")) or
          (not testSide("right") and not testSide("front") and testSide("left")) then
       redstone.setOutput("back",true)
       redstone.setBundledOutput("back",255)
     end
   else
       redstone.setOutput("back",false)
       redstone.setBundledOutput("back",0)
   end
   os.pullEvent("redstone")
end