Startup:263: attempt to concatenate nil and string error

Hello,

I need help to fix this issue. I built a nuclear reactor and the reactor is controlled by the computer from the mod computercraft. While Registering the reactors to computer. the error pops up: startup:263: attempt to concatenate nil and string. I did everything what i can do to fix this issue but didn't get it.

Here is the code from startup:

function everything()
print('Waiting for possible chunk loading...')
sleep(2) --wait for chunk loading

--------configurations
--sensors--
AR_Sensor_Prefix=''
side=sensors.getController()
--actuators--
BC_side='back'
BCbustransceiver_side='bottom'
ACcolors={c_power=colors.purple,c_ice=colors.blue,c_uran=colors.lime,c_retriever=colors.brown}
mon_side='top' --it is optional to have a monitor

--id tags--
ucell_name='item.itemCellUran'--replace 0 by number till
uneardepleted_name='item.itemCellUranEmpty'
ureenriched_name='item.itemCellUranEnriched'
ice_name='tile.ice'
--------configurations end
message={}
function update(arg)
term.clear()
if #arg>0 then message=arg end
for i, v in ipairs(message) do print(v) end
if power==true then s='On' else s='Off' end
print('Power '..s)
print('maxUran:'..tostring(maxUran)..'. To depletion:'..tostring((10000-maxUran-params.Umin)/params.Uspeed/60)..' mn.')
print('min_iceslots:'..tostring(min_iceslots))
print('ice_missing:'..tostring(ice_missing))
print('n_to_withdraw:'..tostring(n_to_withdraw))
print('n_slots_free:'..tostring(n_slots_free))
params=getSavedParams()
updateReactorsState()
for i,reactor in pairs(reactors) do
  if not compress(reactor.ice_slots_start)==compress(reactor.ice_slots) then
    error('Ice slots changed in Reactor '..reactor.name..'. Pos:'..reactor.pos)
  end
end
end
function getReactors()
reactors={}
for i,sensor in ipairs(sensors.getSensors(side)) do
  if sensor:sub(0,#AR_Sensor_Prefix)==AR_Sensor_Prefix then
  if (not sensors.getAvailableReadings(side, sensor)[1]=='No Readings found') or sensors.getAvailableReadings(side, sensor)[1]=='TargetInfo' then
  if sensors.getSensorInfo(side, sensor).cardType=='IndustrialCraft2 SensorModule' then
   sensors.setSensorRange(side,sensor,'8')
   for j, target in ipairs(sensors.getAvailableTargetsforProbe(side,sensor,'ReactorContent')) do
    name='AR Reactor '..sensor:match('^'..AR_Sensor_Prefix..'(.*)')..' '..tostring(i)..':'..tostring(j)
    size=6*(3+tonumber(sensors.getSensorReadingAsDict(side,sensor,target,'Reactor').size))
    pos=target:match('(%d+,%d+,%d+)$')
    reactor={name=name, target=target, sensor=sensor, size=size, pos=pos}
    reactors[target]=reactor
   end
  end end end
end
new_reactors={}
for i,v in pairs(reactors) do new_reactors[#new_reactors+1]=v end
reactors=new_reactors
if #reactors==0 then print('No reactors found. Check adjacency of sensors, type of card and sensors name prefix:'..AR_Sensor_Prefix) end
return reactors
end


function UpdateReactorState(reactor)
local n_slots_filled=0
local ice_missing=0
local n_to_withdraw=0
local maxUran=0
local ice_slots={}
local min_iceslots=64

for i,v in pairs(sensors.getSensorReadingAsDict(side,reactor.sensor,reactor.target,'ReactorContent')) do
  n_slots_filled=n_slots_filled+1
  if v:sub(-2-#ice_name,-3)==ice_name then
   qty=tonumber(string.match(v,'^(%d*)%*'))
   ice_missing=ice_missing+64-qty
   ice_slots[#ice_slots+1]=i
   min_iceslots=math.min(min_iceslots,qty)
  elseif v:sub(-2-#uneardepleted_name,-3)==uneardepleted_name then
   n_to_withdraw=n_to_withdraw+tonumber(v:match('^(%d+)%*'))
  elseif v:sub(-2-#ureenriched_name,-3)==ureenriched_name then
   n_to_withdraw=n_to_withdraw+tonumber(v:match('^(%d+)%*'))
  elseif v:match(ucell_name..'@') then
   m=v:match('@(%d+)$')
   if m==nil then m=0 end
   maxUran=math.max(m,maxUran)
  end
end
table.sort(ice_slots)
reactor.ice_missing=ice_missing
reactor.n_to_withdraw=n_to_withdraw
reactor.n_slots_filled=n_slots_filled
reactor.maxUran=maxUran
reactor.ice_slots=ice_slots
reactor.min_iceslots=min_iceslots
end
function aggregateReactors(reactors)
if #reactors==0 then error('No reactors to aggregate.') end
t_size=0
for i, reactor in pairs(reactors) do
   UpdateReactorState(reactor)
   reactor.ice_slots_start=reactor.ice_slots
   t_size=t_size+reactor.size
end
print('Reactors aggregated. Total size:'..tostring(t_size))
end
function compress(a)
s=''
for i=1,#a do
  s=s..a[i]
end
return s
end
function updateReactorsState()
ice_missing=0
n_to_withdraw=0
n_slots_filled=0
maxUran=0
min_iceslots=64
n_t_ice_slots=0
for i,reactor in pairs(reactors) do
  UpdateReactorState(reactor)
  ice_missing=ice_missing+reactor.ice_missing
  n_to_withdraw=n_to_withdraw+reactor.n_to_withdraw
  n_slots_filled=n_slots_filled+reactor.n_slots_filled
  maxUran=math.max(reactor.maxUran,maxUran)
  min_iceslots=math.min(min_iceslots,reactor.min_iceslots)
  n_t_ice_slots=n_t_ice_slots+#reactor.ice_slots
end
n_slots_free=t_size-n_slots_filled
end

message={}

rs.setBundledOutput(BC_side,0)
BCnumbers={'1','2','4','8','16','32','64','128','256','512','1024','2048','4096','8192','16384','32768'}
BCstate={}
for i=1,#BCnumbers do
BCstate[BCnumbers[i]]=false
end
function setColor(c,Bool)
BCstate[tostring(c)]=Bool
BCnumber=0
for i=1,#BCnumbers do
  if BCstate[BCnumbers[i]]==true then
   BCnumber=BCnumber+tonumber(BCnumbers[i])
  end
end
rs.setBundledOutput(BC_side,BCnumber)
end
power=false
function Power(Bool)
    if not (power==Bool) then
	 power=Bool
  setColor(ACcolors.c_power,Bool)
  if Bool==true then s='On' else s='Off' end
  print('Power '..s)
end
end
function Ice(Bool)
setColor(ACcolors.c_ice,Bool)
end
function Retriever(Bool)
setColor(ACcolors.c_retriever,Bool)
end
function Uran(Bool)
setColor(ACcolors.c_uran,Bool)
end
--fill functions--
function fillUran()
update{}
if n_slots_free > 0 then
  update{'Inserting '..tostring(n_slots_free)..' Uranium cells.'}
  Uran(true)
  while n_slots_free>0 do sleep(params.main_delay) update{} end
  Uran(false)
end
end
function retrieve()
update{}
if n_to_withdraw>0 then
  update{'Retrieving '..tostring(n_to_withdraw)..' near depleted and/or re-enriched cells.'}
  Retriever(true)
  while n_to_withdraw>0 do sleep(params.main_delay) update{} end
  Retriever(false)
end
end
function fillIce()
update{'Filling with ice.'}
if ice_missing>0 then
  Ice(true)
  while ice_missing>0 do sleep(params.main_delay) update{} end
  Ice(false)
end
end

function auto()
update{}
while true do
  while 10000-maxUran<=params.Umin do
	  Power(false)
	  update{'Almost depleted cells detected. Entering depletion cycle'}
	  sleep(params.excess_ice_delay)
	  retrieve()
   fillUran()
   fillIce()
   if 10000-maxUran<params.Umin then
    update{}
    sleep(params.excess_ice_delay)
    Power(true)
    ti=os.clock()
    sleep_duration=(10000-maxUran)/params.Uspeed+params.depletion_delay
    while os.clock()-ti<sleep_duration do
	 update{}
	 sleep(params.main_delay)
    end
    Power(false)
    update{}
   end
  end
  if (n_slots_free>0 or n_to_withdraw>0) then
   Power(false)
   update{'Empty slots near-depleted/re-enriched cells detected.'}
	  sleep(params.excess_ice_delay)
   retrieve()
   fillUran()
  end
  fillIce()
  while (not (10000-maxUran<=params.Umin)) and n_slots_free==0 and n_to_withdraw==0 do
   update{'In main loop.'}
	  Ice(true)
	  Power(true)
	  sleep(params.main_delay)
  end
  Ice(false)
  Power(false)
end
end
function saveReactors(reactors)
file=fs.open('disk/AR_reactors','w')
for i,reactor in  pairs(reactors) do
  s='Entry{name=\''..reactor.name..'\', target=\''..reactor.target..'\', sensor=\''..reactor.sensor..'\', size=\''..reactor.size..'\', pos=\''..reactor.pos..'\', ice_slots_start=\''..compress(reactor.ice_slots_start)..'\'}'
  file.writeLine(s)
end
file.close()
end
function getSavedReactors()
local reactors = {}
    function Entry (B)/> reactors[#reactors+1] = b  end
    dofile("disk/AR_reactors")
    for i, r in pairs(reactors) do
	 r.size=tonumber(r.size)
    end
    return reactors
end

function saveParams(params)
file=fs.open('disk/AR_params','w')
for i,v in  pairs(params) do
  s='Entry{\''..tostring(i)..'\',\''..tostring(v)..'\'}'
  file.writeLine(s)
end
file.close()
end
function getSavedParams()
params = {}
if fs.exists("disk/AR_params") then
	 function Entry (B)/> params[b[1]]=tonumber(b[2])  end
	 dofile("disk/AR_params")
    end
    return params
end
if fs.exists('disk/AR_reactors') then
print('Found saved reactors in disk/AR_reactors.\nTo reset and choose reactors, delete the file and reboot.')
reactors=getSavedReactors()
else
print('List of reactors not found. Waiting for human interaction, press enter to proceed.')
read()
pre_reactors=getReactors()
reactors={}
print('Listing reactors, enter \y\+enter to confirm or \'n\'+enter to discard.')
for i, reactor in pairs(pre_reactors) do
  for n, v in pairs(reactor) do print(n..':'..v) end
  r=0 while not (r=='y' or r=='n') do r=tostring(read()) end
  print('Choice registed')
  if r=='y' then print('Keeping reactor for AR.') reactors[i]=reactor end
end
end
aggregateReactors(reactors)
updateReactorsState()
saveReactors(reactors)
print('Reactors saved to disk/AR_reactors')
rs.setOutput(BCbustransceiver_side,true)

if fs.exists('disk/AR_params') then
print('Found operational parameters file.\nTo modify, edit disk/AR_params and save.')
params=getSavedParams()
else
print('List of parameters not found. Waiting for human interaction, press enter to proceed.')
read()
function check_edit(table)
  for i,v in pairs(table) do
   print(i)
   print('set to:'..tostring(v))
   print('Edit?y/n+enter')
   repeat r=read() until (r=='y' or r=='n')
   if tostring(r)=='y' then
   print('Write the desired value, and press enter.')
    v=tonumber(tostring(read()))
   end
   params[i]=v
  end
end
params={}
aggregateReactors(reactors)
updateReactorsState()
check_edit({Umin=20,Uspeed=1,excess_ice_delay=5,depletion_delay=5,main_delay=5})
saveParams(params)
print('Parameters saved to disk/AR_params')
end
aggregateReactors(reactors)
if peripheral.isPresent('top') then if peripheral.getType('top')=='monitor' then monitor=peripheral.wrap('top') term.redirect(monitor) end end
auto()
end
local status, err = pcall(everything)
if not status then rs.setOutput(BCbustransceiver_side,false) print(err) end

Here is the line 263 of the startup file:

s='Entry{name=\''..reactor.name..'\', target=\''..reactor.target..'\', sensor=\''..reactor.sensor..'\', size=\''..reactor.size..'\', pos=\''..reactor.pos..'\', ice_slots_start=\''..compress(reactor.ice_slots_start)..'\'}'

Here is a screenshot about it:

The thing is, either copy/paste doesn't work or your 263rd line indeed is an "end". The only thing that possibly attempt to call nil around there is the .writeLine call, which would mean a file handle which is nil (couldn't open the file on line 259). Try printing "type(file)" after line 259, and tell us the result.

In case you think I'm wrong and line 263 is not only an "end", put your full code up to pastebin. I've already uploaded it, but line 263 is only an "end" there as well…

EDIT: Sorry, I've misread it - you're not getting "attemp to call nil" but string-nil-concat… Anyways, check the line number, please…

the line 263 i posted is the error
now getting startup:243: attempt to concatenate nil and string see pastebin line 243 the same code i posted

EDIT: Here http://pastebin.com/Kk2EQYdV

Put these lines after line 242:

print("--- Iteration key: " .. tostring(i))
print(type(reactor.name))
print(type(reactor.target))
print(type(reactor.sensor))
print(type(reactor.size))
print(type(reactor.pos))
print(type(compress(reactor.ice_slots_start)))
print("--- End iteration")

Tell us the result. You could easily solve your problem on your own using this technique called debugging.

Thank you
the code you give me worked to fix to concatenate nil and string but now im getting startup:276: attempt to index ? (a nil value)

I have to reindent your code. This is gonna take a little bit of time. And by the was, that 8 lines of debuggins wasn't meant to or was able to solve your problem at line 243…

LBPHacker, on 04 July 2013 - 03:11 PM said:

I have to reindent your code. This is gonna take a little bit of time. And by the was, that 8 lines of debuggins wasn't meant to or was able to solve your problem at line 243…

Im really thankful for your help.

One of the reactor's values is nil. An easy way to fix this is to replace that line with

s='Entry{name=\''..(reactor.name or "nil")..'\', target=\''..(reactor.target or "nil")..'\', sensor=\''..(reactor.sensor or "nil")..'\', size=\''..(reactor.size or "nil")..'\', pos=\''..(reactor.pos or "nil")..'\', ice_slots_start=\''..(compress(reactor.ice_slots_start) or "nil")..'\'}'

and see which says nil

EDIT: sorry, I should probably explain what I did there. Here we go

In Lua the or statement is used primarily in if statements

if 1==2 or 3==3 then
  --code
end

will work fine but what the or statement really does is check if the value before it is nil or false, if it is either then it returns the second value instead. Here is an example of how this works

print(myVar or "var is nil/false")
local myVar=false
print(myVar or "var is nil/false")
myVar="randomValue"
print(myVar or "var is nil/false")

it is also very useful when checking values

reactor=reactor or {}

will not change reactor if it has a value but if reactor is nil or false it will set it to be an empty table

KaoS, on 04 July 2013 - 03:18 PM said:

One of the reactor's values is nil. An easy way to fix this is to replace that line with

s='Entry{name=\''..(reactor.name or "nil")..'\', target=\''..(reactor.target or "nil")..'\', sensor=\''..(reactor.sensor or "nil")..'\', size=\''..(reactor.size or "nil")..'\', pos=\''..(reactor.pos or "nil")..'\', ice_slots_start=\''..(compress(reactor.ice_slots_start) or "nil")..'\'}'

and see which says nil

startup:269: attempt to index ? (a nil value)

Here the pastebin: http://pastebin.com/eGLR7Vpx

what is that table b?

function Entry (B ) params[b[1]]=tonumber(b[2]) end

EDIT: I think the B in the function parameters should prolly be lowercase

hello,

:D/> Thanks Kaos
with this code

s='Entry{name=\''..(reactor.name or "nil")..'\', target=\''..(reactor.target or "nil")..'\', sensor=\''..(reactor.sensor or "nil")..'\', size=\''..(reactor.size or "nil")..'\', pos=\''..(reactor.pos or "nil")..'\', ice_slots_start=\''..(compress(reactor.ice_slots_start) or "nil")..'\'}'

worked. A thanks for the helpers:: Kaos, LPBHacker