ChunkIterator with next

[sikian]

Hi guys,

I've been trying to use the ChunkGenerator as an iterator and have finally managed to do so in a somewhat elegant way. However, I'm still not sure about some things. Maybe someone can help me out with this!
As for why I'm using it as an iterator is due to the fact that I want to get some info from all the chunks, but I think limiting the chunks checked by tick is probably a good way to go.

Let's start:
From http://lua-api.factorio.com/latest/LuaC ... rator.html, we can see that some_surface.get_chunks() provides a ChunkIterator.

From various documentations I've seen, getting the next element of an iterator can be reached either calling the iterator function or next (I might be waaaay off here, but that was my conclusion of what I read).
So I set off trying both things:

Code: Select all

local chunk_iter = surface.get_chunks()
local chunk = next(chunk_iter)
print(chunk, chunk.x, chunk.y)

This yields:

__self nil nil

So, wrong step.

Let's try with calling the iterator:

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local chunk_iter = surface.get_chunks()
local chunk = chunk_iter(1,1)
print(chunk, chunk.x, chunk.y)

The two arguments was what I found worked (as the function arity was complaining).
This seems to work, but now comes the question: what do those arguments mean?

Thanks in advance and sorry if this might seem a stupid question!

[darkfrei]

Code: Select all

/c local surface = game.player.surface
for c in surface.get_chunks() do
	local position = surface.find_non_colliding_position("biter-spawner", {x=c.x*32+16, y=c.y*32+16}, 10, 3)
	if position and surface.is_chunk_generated(c) then
		surface.create_entity{name="biter-spawner", position=position}
	end
end

Chunk is a table, chunk.x and chunk.y are coordinates of this chunk. In this example c is a chunk in all chunks.

[DaveMcW]

The arguments do not seem to do anything, you just need to have 2 of them.

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local chunk = chunk_iter(nil,nil)

[Rseding91]

The arguments do not seem to do anything, you just need to have 2 of them.

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local chunk = chunk_iter(nil,nil)

In standard Lua "next" the call operator takes the last index retrieved and the thing to get the "next of last index" from. The LuaChunkIterator uses neither of those and each call simply gives the next chunk position while storing the state internally.

When you do this:

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for k,v in pairs(game.players) do ... end

That's actually doing something like this:

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local players = game.players
local k, v = next(nil, players)

while (k ~= nil) do
  ...
  k, v = next(k, players)
end

[DaveMcW]

The LuaChunkIterator uses neither of those

Any chance of fixing the error when you don't provide 2 arguments then?

[BenSeidel]

The LuaChunkIterator uses neither of those

Any chance of fixing the error when you don't provide 2 arguments then?

The LuaChunkIterator is not an Iterator, but an Iterable, hence the issues when using it. It's not about the arguments supplied.

[sikian]

Hey guys, thanks for your answers, but I yet don't understand how to use LuaChunkIterator to iterate through the chunks without a loop, but using something similar to next().

Thanks

[prg]

If you use next() on the return value of get_chunks(), you really only get the __self = "userdata: ..." thing out of it. The interesting behavior is implemented using metamethods so it can be used in a generic for. You can turn that into a while loop as mentioned in the manual like

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f, _, var = game.player.surface.get_chunks()
while true do
    var = f(nil, var)
    if var == nil then break end
    print(serpent.block(var))
end

if you like that better, but not much else you can do with it that I can see.