local _G = _G

[Sweetsour]

When peeking into certain addons' code, I notice a lot of globals being set to locals, one commonly being the following:

local tonumber, pairs, ipairs, error, unpack, select, tostring = tonumber, pairs, ipairs, error, unpack, select, tostring

I was curious, does this save memory space or something?

[Resike]

Originally Posted by Sweetsour When peeking into certain addons' code, I notice a lot of globals being set to locals, one commonly being the following: local tonumber, pairs, ipairs, error, unpack, select, tostring = tonumber, pairs, ipairs, error, unpack, select, tostring I was curious, does this save memory space or something?

Sacrifices some memory usage for a tiny bit of performace gain.

[VincentSDSH]

Probably needs a bit of conceptual explanation for new authors who'll run across this question.

Lua is a maze of tables. When you call a function (say, 'pairs') it goes through the function list to find it, traversing the tree's branches till it does. Its vars in this usage are pointers to table locations that contain the function (unlike some languages where an = is a value copy) so that makes things both easier or harder depending on what you're trying to achieve.

local pairs = pairs says "store the location of 'pairs' in this local var called 'pairs' (or anything you like) so you don't have to look for it.

You'll see the same with a lot of Ace addons: local sdbc, layout = self.db.char, self.db.global.customization.windows.layout

When authors have a lot of loops or a lot of calls and actions, they'll trade memory for performance b/c those little lookups add up amazingly fast, especially when you run a lot of addons.

[Seerah]

Keep in mind that the performance gains are very minuscule. Only worth it if you are calling the upvalued functions/table lookups many times when optimized performance is best - in combat, an OnUpdate script, etc.

[Sweetsour]

Thanks for all the info, it all makes a lot more sense