Re: Lua 5.1 upvalues

[Rob Hoelz <rob@...>]

They don't really conflict at all.  You're storing a reference to a
table; i.e. a memory address.  If you share that address between two
closures, they can both change the contents stored at that address.
If you store a number in that upvalue instead, altering it in one
closure wouldn't affect the upvalue of the other.  It's kind of like
the difference between passing an int to a C function versus passing
a pointer to a struct to a C function.

-Rob

On Fri, 08 Apr 2011 23:04:36 +0200
Anthony Howe <achowe+lua@snert.com> wrote:

> On 08/04/2011 21:16, Rob Hoelz whispered from the shadows...:
> > If you want C closures to share values, you could store a table as
> > an upvalue, store your values in there, and set the same table as an
> > upvalue for the closures.
> 
> Ugh. One person says no. Another suggests the very thing I want to try
> that prompted the question.
> 
> In 5.1 does...
> 
> 	lua_newtable(L);
> 	lua_pushvalue(L, -1);
> 	lua_pushcclosure(L, &foobar, 1);
> 	lua_pushcclosure(L, &barblat, 1);
> 
> 	-- rinse & repeat
> 
> Work? Can more than one C function share a single upvalue? I ask
> because something along these lines has been mentioned in Lua 5.2 as
> an alternative to environments or some such without any examples. So
> I'm unclear as to whether this is possible in 5.1 and/or 5.2.
> 
> So far I have conflicting answers.
> 
> > 
> > -Rob
> > 
> > On Fri, 8 Apr 2011 15:05:31 -0400
> > Patrick Donnelly <batrick@batbytes.com> wrote:
> > 
> >> On Fri, Apr 8, 2011 at 1:46 PM, Anthony Howe <achowe+lua@snert.com>
> >> wrote:
> >>> Can Lua 5.1 upvalues be associated with more than one C closure?
> >>
> >> No.
> >>
> > 
>

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