How to iterate through a tuple?

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#1

As the title says.

I’m trying to make a variable collection thing using attributes, it works by putting attributes that are available into a table and then it’s unpacked for other parts of my script to use:

local VariableTable = {}
local CurrentVariableNumber = 1
local VariableToAdd = CacheFolder:GetAttribute("Variable"..CurrentVariableNumber)
if VariableToAdd then
	table.insert(VariableTable, CurrentVariableNumber, VariableToAdd)
	CurrentVariableNumber = CurrentVariableNumber+1
end
return VariableTable

the problem with attributes is that they don’t store nil values in themselves, so if I needed a nil value to be returned it won’t be returned because you can’t put nil values in tables either, which is a problem because I use table.unpack after getting the table result.

My idea right now is to make attributes that need to have nil values have a string nil and have it become nil if detected in a dictionary, my issue right now is trying to loop through tuples, how do you iterate through a tuple from a table.unpack?

Edit: Current Scenario I’m trying to solve

I have seven variables made that each fire SetAttribute()
Variables 1-4 are random numbers.
Variables 5-6 are nil. They are needed readable nil values.
Variable 7 is a random number. This is a needed value.
Variables 5-7 aren’t being returned from table.unpack from my variable collection, they are being indexed correctly with Table[5] = nil, Table[6] = nil, Table[7] = 25 but only Table[1-4] gets readable printed back and nothing appears after 5-7.

#2

I’m confused, couldn’t you just iterate through before unpacking and use the pairs iterator which works with nil values?

local t = {1;2;3;4;5;nil;nil,8}
for i,v in pairs(t) do
    print(v) -- prints 1-8 except 6 and 7
end

print(unpack(t)) -- prints the tuple instead of the table except for 8
#3

There’s already a function for this.

2 Likes
#4

When I put nil inside of a table it doesn’t get seen by the script and the rest of the table is cut off. However if I replace nil with a string it can be used inside of tables.

#5

By putting it inside I mean indexing a table as a nil value like Table[1] = nil you can’t put a nil inside a table so if you do Table[1] = "Chicken" Table[2] = nil Table[7] = "Nuggets" print(unpack(Table)) it doesn’t print 7 or the nils in between 2-6.

#6

not entirely sure, but I think this solves your issue. I haven’t used the Select() function

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#7

Pairs doesn’t care about nil values though. You can use that to iterate over all of the values and ignore the nil ones.

#8

If your table will have nil in it, then you should use pairs instead of ipairs. Although it won’t be in order, I don’t know why you have nil in a table, so it shouldn’t affect it much.

#9

You may want to read this great article:

https://benaiah.me/posts/everything-you-didnt-want-to-know-about-lua-multivals/

To summarize: don’t bother with tuples in most cases, they’re sort of half-datatypes in lua that have some weird behavior.