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- Subject: Re: _SELF and _SUPER
- From: "Soni L." <fakedme@...>
- Date: Thu, 4 Aug 2016 17:11:50 -0300
On 04/08/16 04:47 PM, Nagaev Boris wrote:
On Thu, Aug 4, 2016 at 7:54 PM, Soni L. <email@example.com> wrote:
Can we get _SELF and _SUPER?
local x = 1
local x = 2
print(_SUPER.x) --> 1
if x < 0 then error() end
if x == 0 then return end
end, 3) --> 3; 2; 1;
For performance, they would be translated by the compiler. Passing _SUPER
around would copy all upvalues into a table, but for simplicity changing
this table wouldn't change upvalues (e.g. no current syntactic construct can
create a metatable).
_SELF and _SUPER would be indexable and callable.
Let me check that I understand you correctly.
_SELF would be callable and _SUPER would be indexable.
No you can use _SELF.name as an alias for the local `name` (simple
compiler optimizations can turn `_SELF.name` (as well as
`_SELF["name"]`) into just `name`).
You can also call _SUPER.
You can also do _SUPER._SUPER.
Note that the main chunk wouldn't have _SUPER (but it would have _SELF).
Can _SUPER be indexed with a value not known at compile time?
local xx = 1
Except for the do..end and _SUPER part, yes, that would work.
local xx = 1
_SELF[string.rep("x", 2)] = 3
print(xx) --> 1, not 3
Because for dynamic assignments _SELF would need a metatable. No current
Lua opcode ever produces a table that already has a metatable. _SELF and
_SUPER are special names however, which means they can behave specially
(e.g. one behaviour for _SELF.x and other compile-time constants,
another behaviour for _SELF[x] and other runtime values).
Another option would be to introduce "indirection" opcodes. E.g.
_SELF[x] = other
would translate into
GETTABLE (internal) [x] reg -- plain old gettable, I forgot the syntax;
(internal) would be a reserved table the compiler generates for things
MOVEI reg [other] -- R(R(A)) =: R(B)
Note the R(R(A)) part.
(No idea what to say next. Idk, I'm just rambling I guess .-.)
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