Re: Custom extensions to Lua

[Rici Lake <lua@...>]

On 10-Aug-05, at 3:50 PM, Glenn Maynard wrote:
> > Well, beauty is in the eye of the beholder :) Many people might prefer
> > something like:
> >
> >   synchronized int value;
> >
> > although that doesn't give you the option of forgetting to use the
> > locked version :)
>
> This requires specific support from the language itself to implement, 
> and
> means the compiler itself has to understand locking, compared to the 
> generic
> template solution.

Yes, that's true. On the other hand, it means that a compiler aware of 
concurrency has to do quite a bit of difficult analysis in order to 
optimise locking, which would have been easier had the declaration been 
explicit.

You could say the same thing about exceptions, really. Why should the 
compiler provide specific support when it could be achieved in the 
standard library (with setjmp and friends)?

The question of which features should be included in a language and 
which ones should be relegated to library implementation is not easy, 
and every language draws its own line. Clearly, there are languages 
which prefer the synchronization declaration, and it appears that there 
are programmers who are quite happy to use those languages. :)

> You can't forget anything if you use a template type that doesn't 
> initialize
> from a pointer:
>
>   locked<int> value = 1;
>   value = 2;

Yes, again. In which case, the use of the synchronized attribute would 
have been precisely equivalent, aside from the issue of whether it 
should be in the compiler, in a standard template library, or even 
implemented with a preprocessor.

> The license doesn't require renaming on modification.  I don't think 
> that's
> a very good restriction, especially given that modifying Lua to suit 
> the
> particular needs of a project is actively encouraged.  It wouldn't be
> very nice to publically fork Lua and not rename it (confusing), but 
> there's
> nothing wrong with a project using a heavily modified core and still 
> saying
> "we use Lua".

Hmm. I guess I was still thinking of the Lua 4.0 licence.