spawnturret.lua

local statelist = {
  ["top"] = rs.getInput("top"),
  ["front"] = rs.getInput("front"),
  ["left"] = rs.getInput("left"),
  ["right"] = rs.getInput("right"),
  ["back"] = rs.getInput("back"),
  ["bottom"] = rs.getInput("bottom"),
}

local function spawn()
    if commands.blockdata then
        -- User is on at least MineCraft 1.8, snapshot 14w02a.
        commands.exec("summon Skeleton ~0 ~1 ~0 {Equipment:[{id:bow,tag:{ench:[{id:48,lvl:4}]}},{},{},{},{id:iron_helmet}],CustomName:Turret,CustomNameVisible:0,Attributes:[{Name:generic.maxHealth,Base:2},{Name:generic.movementSpeed,Base:0.001},{Name:generic.followRange,Base:32}],PersistenceRequired:1}")
    else
        -- User is on something earlier.
        --commands.exec("summon Skeleton ~0 ~1 ~0 {Equipment:[{id:261,tag:{ench:[{id:48,lvl:4}]}},{},{},{} {id:306}],CustomName:Turret,CustomNameVisible:0,Attributes:[{Name:generic.maxHealth,Base:2},{Name:generic.movementSpeed,Base:0.001} {Name:generic.followRange,Base:32}],PersistenceRequired:1}")
    end
end

while(true) do
    local event = os.pullEvent("redstone")
    for side, state in pairs(statelist) do
        if rs.getInput(side) then
            spawn()
        end
        statelist[side] = rs.getInput(side)
    end
    --spawn()
    os.sleep(1)
end