Re: Lua strings as "atoms"???

[Chris Marrin <chris@...>]

Rici Lake wrote:
> ...
> There was a discussion about this on the mailing list a while back, and 
> the definitive answer from a Lua author was that when it says "the 
> stack", it really means "the stack". That surprised me, too, but the 
> manual is quite clear.
>
> If the string is stored in the registry, it won't be garbage collected. 
> But there is no *official guarantee* that it won't move. There is an 
> *official guarantee* that it won't move if it is on the stack.

Ok, so maybe they were thinking about the now defunct generational 
collector. At any rate, is there any officially sanctioned way of 
handling "atoms" or the equivalent?

> In practice, however, the standard implementation of Lua doesn't use a 
> moving garbage collector, so the code you present is not going to fail 
> with the current Lua version, as far as I know.

Ok, I will do an implementation based on this and isolate it so I can 
muck with it if things change.

> Whether that particular bit of code is faster than doing a pushstring or 
> not, I don't know. I rather suspect it would be faster, at least for 
> long strings. However, if you can use upvalues, you will find them to be 
> faster than registry stashing -- although I rather sadly suspect that 
> upvalues may not survive through the next n versions of Lua for some 
> smallish value of n.

I will test it and let you know...

What would upvalues be replaced with? Surely Lua is not abandoning 
closures! That is one thing that has gotten Lua a lot of press for being 
hip and cutting edge :-)

--
chris marrin                ,""$,
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