LUA and Peripherals (Railcraft)

Hello guys:

a short question, i think the answer is pretty easy, but i cannot find my mistake:

this code:

tank = peripheral.wrap("bottom")
modem = peripheral.wrap("back")
modem.open(1)


while true do
tableInfo = tank.getTanks("unknown")
for key,value in pairs(tableInfo) do
  for x,y in pairs(value) do
	  if x == "amount" then
		percent = math.floor(y / 576000 * 100)
		print(percent, "%")
		modem.transmit(1, 1, percent)
	  end
  end
end
  sleep(2)
end

is working as intended (0 errors) if there is any amount > 0 in the tank, so i tried to get rid of the nil problem with:

tank = peripheral.wrap("bottom")
modem = peripheral.wrap("back")
modem.open(1)


while true do
tableInfo = tank.getTanks("unknown")
for key,value in pairs(tableInfo) do
  for x,y in pairs(value) do
	  if x == "amount" then
		percent = math.floor(y / 576000 * 100)
		print(percent, "%")
		modem.transmit(1, 1, percent)
	
	  else
		print("empty")
		sleep(10)	
	 end
end
end
sleep(2)
end

but here i get always "empty" regardless the amount in it

my thoughts:
* why is in the first code the if - function progressing to "then" and in the 2nd to "else" but i changed nothing in the tank
* if the tank is empty there is no x=="amount" in the table, so the if-function should proceed to "else", or?
* i cannot set y==0 or y==nil or y>0 because if there is no amount in the tank the if - function with x=="amount" is not triggering, or?

How can i bypass this problem?

And a short second question:
can i compare the y-value from each loop? – so that a message or what else is only sent, if the value(amount) changed?


Thx in advance
Wiesl

Split into new topic.

Are you trying to do something like this?

tank = peripheral.wrap("bottom")
modem = peripheral.wrap("back")
modem.open(1)


while true do
    tableInfo = tank.getTanks("unknown")
    for tNum, tInfo in pairs(tableInfo) do
        if tInfo.amount then
            percent = math.floor(tInfo.amount * 100 / tInfo.capacity)
            print(tostring(percent).."%")
            modem.transmit(1, 1, percent)
        end
    end
    sleep(2)
end

There are other ways to interact with tables than iterating through them. I hope this thing has more than one tank in it, or you don't even need the outside for loop.

Sry i donnot understand you completly ;)/>
may i ask a little further?

in your explanation, there is again the problem, that if the "amount" == 0 there is no topic amount in the table, only capacity and pressure, so, i cannot get the variable tinfo.amount. Not = nil nor =0, because she simply didn`t exist i think.

i try to get further in it, but any help would be appreciated.


Thx
Wiesl

P.S.: perhaps a 2nd Question, also:

i think the tableinfo = tanks.getTanks("unknown")
is producing a table like this, or?

tableInfo
–> amount –> 1000
–> capacity –> 50000
etc.

i can make this my own with this code, or?(in just this moment)

tableInfo = {}
tableinfo.amount = 2783
tableinfo.capacity = 576000
tableinfo.name = "Steam"

how can i print for example tableInfo –> amount –> 2783
because

tank = peripheral.wrap("bottom")


tableInfo = tank.getTanks("unknown")
print (tableInfo.amount)

is doing nothing beside a empty row.

How can i get the row amount printed, if i donnot know the exact name, because i didn?t made the table myself, but a programm (like .getTanks("side"))

Thx in Advance
Wiesl

Ok i found something out:
the table is a table in a table with a 1 in front, like
tableInfo–>1–>amount(or capacity)–>value

i donnot know why, but i think it is so configured.

so i can print the amount with:

print(tableInfo[1]["amount"])

ok but my problem is nevertheless:

if the amount is 0, the table doesn´t contain the key "amount", so i cannot make a function with it.

how to say the programm: if there is no key "amount" in table[1] do something??

Wiels

For the purposes of an if/then/else statement, variables count as "true" if they exist, false if they do not.

Lyqyd's example demonstrates this, but you may find this more clear-cut:

if not tableInfo[1]["amount"] then
  print("Looks like there's no \"amount\" key in the table.")
else
  print("There's an \"amount\" key with an assigned value in the table!")
end

thx now it is more clear!!

hope i can configure it now!

the reason you must do

tableInfo[1]

is because it is possible to have blocks with multiple tanks within them, for example think Forestry or Thermal Expansion how there is an output as well as a water level. As such each "tank" gets placed into its own index with its appropriate information.

When someone gives you code to test, please actually test it before you simply declare that it has the same problem as your original code.