What exactly are Locals?

[Jasoco]

I can't seem to figure out what the benefits and limitations of Locals are. I tried Googling for a Lua site but it didn't really describe it helpfully.

What would the difference between these two be?

Code: Select all

variable = value

local variable = value

When should and shouldn't they be used?

[TechnoCat]

Sorry to reference you somewhere else, but...
http://www.lua.org/pil/4.2.html

[Jasoco]

Ah, that maks sense now. Thanks!

[TechnoCat]

I have a question now.
If I use

Code: Select all

foo=1
while foo do
   local foo = foo
   -- code goes here
end

Is there a way to modify the global variable in the same scope after I override a global with a local variable?

[Robin]

use _G.foo

[bartbes]

or using a dynamic name (which is surprisingly useful):

Code: Select all

n = "foo"
_G[n] = "bar"

[Zorbatron]

Man, how can you use lua and not know what local variable is XD?

Usually you only use local variables when you only need to store something temporarily. If you always use globals, not only will you be cluttering the global namespace (meaning there will be a lot of variable name conflicts), you are also using more memory than you should be.

[Jasoco]

I never heard of Lua before I found Löve.

[Robin]

Usually you only use local variables when you only need to store something temporarily. If you always use globals, not only will you be cluttering the global namespace (meaning there will be a lot of variable name conflicts), you are also using more memory than you should be.

Not to mention the speed advantages of using locals.
For example,

Code: Select all

function afunc()
    local dothings = dothings
    dothings()
    dothings()
    dothings()
    dothings()
    dothings()
end

will be faster than

Code: Select all

function afunc()
    dothings()
    dothings()
    dothings()
    dothings()
    dothings()
end

[Zorbatron]

@Robin - Its faster because accessing globals requires lua to use the hash-lookup algorithm on the global table correct?