Computercraft Lua change nil to 0

Question

I am using Computercraft, a Minecraft mod, and I needed help with something. I am attempting to find all peripherals of a type, get the energy from them, and add them together. However, I get a "attempt to perform arithmetic on nill" or something error. Here is my code:

local periList = peripheral.getNames()
energy = 0
totalenergy = 0

for i = 1, #periList do
  if peripheral.getType(periList[i]) == "cofh_thermalexpansion_energycell" then
    local cell = peripheral.wrap(periList[i])
    print(periList[i])
    if cell.getEnergyStored("potato") ~= "nil" then
      energy = cell.getEnergyStored("potato")
      print(cell.getEnergyStored("potato"))
    else
      energy = 0
      print(0)
    end
    totalenergy = totalenergy + energy
  end
end
print(totalenergy)

Sorry, codebox didn't work

Anyways, does anyone know how to fix this?

score 4 · Accepted Answer · answered Sep 04 '14 at 23:39

4

nil and "nil" are two different things.

The former is the nil type "singleton" the latter is a string of three characters. They are not equivalent.

Try dropping the quotes from the if line.

Also you can assign (the potential) nil to energy and then directly energy and set it to 0 if it is nil (or even just use

energy = cell.getEnergyStored("potato") or 0

directly since nil is a "false-y" value so nil or 0 evaluates to 0).

answered Sep 04 '14 at 23:39

Etan Reisner

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Yep, just removing the quotes worked. Thanks! How can I mark as solved? – Wolfie_Waffle Sep 04 '14 at 23:52
@NathanielButterfield There should be a check mark under the voting arrows next to the answer that you can click on to accept the answer. – Etan Reisner Sep 05 '14 at 01:28

Computercraft Lua change nil to 0

1 Answers1