tturn.lua

--Movement Program by Galygious
--Variables
    local tArgs = { ... }
    local dirlist = {'u','l','r'}
--Functions
    local printUsage = function(ecode)
        if ecode == 0 then
            print('Error Code 0\nThis program requires these variables:\narg1 - Direction (u,l,r)')
            do return end
        elseif ecode == 1 then
            print('Error Code 1\nThis program requires these variables:\narg1 - Direction (u,l,r)')
            do return end
        elseif ecode == 2 then
            print('Error Code 2\nThis program requires that variable one be a direction (u,l,r)')
            do return end
        end
    end

    local turtleturn = function(Dir)
        if Dir == 'r' then
                turtle.turnRight()
        elseif Dir == 'l' then
                turtle.turnLeft()
        elseif Dir == 'u' then
            for i=1,2 do
                turtle.turnRight()
            end
        end
    end

    local hasval = function(tab,val)
        for i, value in ipairs(tab) do
            if value == val then
                return true
            end
        end
        return false
    end

--Argument Handling
    if tArgs[1] ~= nil then
        if #tArgs ~= 1 then
            printUsage(1)
        elseif not hasval(dirlist, tArgs[1]) then
            printUsage(2)
        else
            local Dir = tArgs[1]
            turtleturn(Dir)
            return
        end
    else
        printUsage(0)
    end