Getting the highest indexed value in a table

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#1

Hello everybody!

While working on my tower defense game I ran into a problem with tables:
To find the farthest enemy on the track I use waypoint numbers and the enemies’ distances to them to get a table somewhat that has:

  • As the index, the distance between the enemy and the next waypoint
  • As the value, the object value of said enemy

For example:

local distances = {
    [5.12] = --Normal enemy,
    [2.41] = --Speedy enemy,
    [4.23] = --Boss,
}

and so on.

My question is, is there any way I can retrieve the value with the highest index number in the array (In this case, the normal enemy)?

#2

I’d suggest moving away from floating-point indexes, anything that’s not an integer, string or Instance in a table can get messy and weird.

If you really wanna store both the distance and object, consider the format {distance, object} then a simple loop to go through every element to get the highest distance.
Another solution is having two tables, one being [number] = distance then another being [object] = number where the number value in the objects table links to the index of the distance, so finding the distance from the enemy would be Distance[Objects[object]].

If you really wanna stick with this though, here’s a simple bit of code to get the highest distance.

local index
for distance, _ in distances do
    if not index or distance > index then
        index = distance
    end
end

print(index)
print(string.format("The farthest (%i studs away) mob is %s", index, distances[index].Name))

EDIT: In my personal opinion you shouldn’t store the distance at all, calculating distance is very fast and very easy so whenever you actually need to get the highest distance, having a table of all the mobs would be much easier to manage and if anyone were to look at your code (including yourself) it’d be much easier to understand.

1 Like
#3

Use table.sort() and get the first value :slight_smile:

3 Likes
#4

This is too vague. His structure won’t work with table.sort because it gives the values of the table, not the indexes.

This’ll work but also, I don’t understand storing distances in a table unless you’re doing this every frame? It just doesn’t make sense.

#5

you dont need to use dummy variables for tuples if your not going to access the next value ex:

for d in distances do
end
1 Like
#6

here, I made a quick script.

local distances = {
	[5.12] = "Normal enemy",
	[2.41] = "Speedy enemy",
	[4.23] = "Boss",
}

local function _get(highest)
	local wantedIndex = -math.huge

	table.foreach(distances, function(a, _)
		table.foreach(distances, function(b, _)
			wantedIndex = highest and a > b and a > wantedIndex and a or b > wantedIndex and b or wantedIndex
		end)
	end)

	return wantedIndex
end

print(_get(true))
#7

I have no idea why I didn’t think about storing things in a {distance, object} kind of fashion, thanks a lot! I’ll be trying out that script first as changing the table structure would mean changing a lot of other code, but I’ll definitely switch to your first solution later. Thanks again!