Re: Non-lexical (lexical) scoping

["Soni \"They/Them\" L." <fakedme@...>]

On 2018-03-20 01:57 AM, Dirk Laurie wrote:
> 2018-03-20 0:38 GMT+02:00 Soni "They/Them" L. <fakedme@gmail.com>:
> > Let's talk about non-lexical lexical scopings. That is, the ability to undefine variables.
> ,,,
> >    forget a
> ...
> >    local a, a, a = 1, 2, 3
> This assumes something about implementation of multiple assignment
> that Lua does not promise.
> ...

Those are 3 different locals.

local a, a, a = 1, 2, 3

*is*

local a = 1
local a = 2
local a = 3

(however, the order in which they are assigned is undefined [1])

But, this is different from

a, a, a = 1, 2, 3

Which is undefined, and could be any of:

a = 1
a = 2
a = 3

a = 3
a = 2
a = 1

a = 1
a = 3
a = 2

etc, you get the idea.

[1] - Using non-lexical scoping, local a, a, a = 1, 2, 3 could be 
expanded to any of:

local a
local a
local a
do
  forget a
  forget a
  a = 1
end
do
  forget a
  a = 2
end
do
  a = 3
end

-- or

local a
local a
local a
do
  a = 3
end
do
  forget a
  a = 2
end
do
  forget a
  forget a
  a = 1
end

-- etc

They are still 3 locals, declared in order, with the 3 values also 
declared in order.

> > I think this sounds neat. What do you think?
> `forget a` looks evocative [1]. But `pop(a)` is the more usual word
> for this sort of thing.
>
> [1] https://xkcd.com/379/

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