Re: Why does luaL_openlibs invoke the interpreter?

["Alex Davies" <alex.mania@...>]

Dustin Juliano wrote:
> 1) Why invoke the interpreter when you can directly call these  function 
> pointers to initialize the library, at will?
> 2) Why are the luaopen_* (luaopen_base, luaopen_package, ..., 
> luaopen_debug) all Lua C Library functions? That is, why do they not  just 
> perform their intended purpose without having to expose  themselves to Lua 
> at all?

I'd say the main reason is is that they can push arbitrary number of results 
on to the stack.
Ie base pushes 2, and the rest 1. Future packages may push 0 or 30. Did you 
notice that
your modified function messes the stack? :).  And should Lua ever have more 
then 20
packages, or a package which pushes lots of results, it'll cause a Lua stack 
overlua.
The call is just proper stack handling - you specify how many results you 
want, you know
where the stack is after the call.

There may be another reason, but that's the first that comes to mind.

Anyway, I'm curious why you're worried about the extra function calls? :)

If via some scenario I can't imagine it's become a bottleneck, you could 
replace the
pushcfunction, pushstring, and call with a regular c call and a 
lua_settop(L, 0), at the
cost of some more ambiguity and less consistency with Lua :).

- Alex