Hi Soni,
On Thu, Jun 20, 2019 at 12:18 PM Soni "They/Them" L. <fakedme@gmail.com> wrote:
> On 2019-06-20 4:06 p.m., Hugo Musso Gualandi wrote:
> > In Python the equivalent metamethod is called __exit__
> >
> > (There is also a corresponding method called __enter__, which is called at the start of the scope)
> >
> >
> >
> > >Actually it would be nice if someone could come up with a word that
> > >coul
> > >express the real concept clearly. For example: "at_scope_end" (or and
> > >"__at_scope_end" as a metamethod. Of course those are UGLY.
> > >
> > >Maybe "atend"? It's more explicit than "toclose" since actually
> > >describes that something happens when execution flow reaches the "end"
> > >keyword. "__atend" is not bad as a metamethod.
> >
>
> local <with> foo = bar --> calls bar's __enter metamethod?
> end --> calls bar's __exit metamethod?
>
> this also has the benefit of handling nested scopes as well, I guess?
We don't need Python's cumbersome "with" semantics as Lua has real
variable scoping. See also [1].
Also thinking about [2] more, where I proposed "bind" instead of
"toclose", I'm wondering if Lua should embrace binding the value's
lifetime to the variable (local) by calling __gc instead of __close.
Is there a good use-case for a value whose lifetime persists after
__close? If Lua calls __gc in a deterministic way, it resolves the
same issues and it can mark the value such that it no longer needs the
extra __gc cycle for finalization (IIRC how that works).
[1] http://lua-users.org/lists/lua-l/2018-07/msg00463.html
[2] http://lua-users.org/lists/lua-l/2019-06/msg00405.html
--
Patrick Donnelly
I disagree with tying this feature to the garbage collector. The current design is recursive; every opening has a corresponding close. Making it part of the garbage collector would mean that no matter how many openings you have, there will only ever be one close.
/s/ Adam
