Variable Number of Arguments table

Question

In lua I'm using someone elses function that takes variable number of arguments. What I would like to be able to do is build the argument list via loop. Is this possible?

Example function:

printResult = ""

function print (...)
  for i,v in ipairs(arg) do
    printResult = printResult .. tostring(v) .. "\t"
  end
  printResult = printResult .. "\n"
end

I tried

print({"test","test2"})

But that just passes one argument (the table) to the function

Like I said it's not my function. But I tried what you suggested in test function but the result was the same — Coder547
– Coder547, Commented Oct 5, 2019 at 15:21

Kaleb Barrett · Accepted Answer · 2019-10-05 22:12:09Z

1

You are looking for the table.unpack function. You can build the arguments to the vararg function you want to call in a table. Calling table.unpack on the table will expand the table into an argument list. Like so,

args = {}
for i = 1, 4 do
    args[#args+1] = i * i * math.pi
end

print(table.unpack(args))

Also, you will need in the print function you posted to gather all those arguments into the arg list that you are using...

function print (...)
  printResult = ""
  arg = {...}
  for i,v in ipairs(arg) do
    printResult = printResult .. tostring(v) .. "\t"
  end
  printResult = printResult .. "\n"
  return printResult
end

Finally, there is already a way to accomplish what you are trying to do using table.concat.

function print(...)
    return table.concat({...}, "\t").."\n"
end

answered Oct 5, 2019 at 22:12

Kaleb Barrett

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