Re: Local and Global Variables
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- Subject: Re: Local and Global Variables
- From: Doug Currie <doug.currie@...>
- Date: 2013年4月26日 11:48:45 -0400
On Apr 26, 2013, at 7:13 AM, Thomas Jericke <tjericke@indel.ch> wrote:
> To me there are still some problems regarding scoping with this, consider:
>
> if someboolean then
> global myvar = 0
> end
>
> print(myvar) -- Is this valid?
>
> Probably the most consistent way would be, that scoping is used for globals too and you would have to do this:
>
> global myvar
>
> if someboolean then
> myvar = 0
> global g2
> end
>
> print(myvar) -- ok
> g2 = 0 -- error
If this is what you want, then the local and global keywords mean the same thing. In expression oriented languages of the ML family, this keyword is called val. It declares a new value in the present scope. So your example becomes:
val myvar
if someboolean then
myvar = 0
val g2 = 7
end
I like this approach, but I am not advocating a change to Lua.
This can also be accomplished with a new operator. In mathematics, := is often used for definitions.
myvar := nil -- global declaration and initialization
if someboolean then
myvar = 0 -- assignment
g2 := 7 -- local declaration and initialization
end
I am not advocating this either, but it may spark some derivative language experiments.
e