Re: [ANN] Lua 5.4.0 (work1) now available

On Tue, Mar 13, 2018 at 10:19 PM, Russell Haley <russ.haley@gmail.com> wrote:

Hi Lua Team,

When compiled as normal and run through the VS 2017 debugger I get a kernelbase exception when I hit Ctrl+C. I don't get that in 5.1 or 5.3.

"Exception thrown at 0x00007FFEDA4CFA2B (KernelBase.dll) in lua.exe: 0x40010005: Control-C. occurred"

In don't have kernelbase.pdb handy so I can't give you too much more (get it? Cause the OS is Binary? lolz! Oh Visual Studio, you are such a comedian.). :-/

Also if I just type undef in the interpreter it waits for more input:

Lua 5.4.0 (work1) Copyright (C) 1994-2018 Lua.org, PUC-Rio
> undef
>>

Just reporting that in case it's unexpected.

> undef = function() print('hello lua team') end

stdin:1: syntax error near '='

> type(undef)

stdin:1: 'undef' is not a value!!

> type(ipairs)

function

> type(type)

function

> type(_VERSION)

string

> type(for)

stdin:1: unexpected symbol near 'for'

Is your error message for undef just for the work release? I ask because it seems to me you've had to break your data types to fit this in. It's not a keyword, but it's not a data type either. Can you explain why this is really better than a table.remove(t,i) function or the prior suggestion by Tomas?

Turning LUA_NILINTABLE on shortly to play.

Also, thanks for the great language.

Russ

On Tue, Mar 13, 2018 at 9:55 PM, Coda Highland <chighland@gmail.com> wrote:
On Tue, Mar 13, 2018 at 11:39 PM, Russell Haley <russ.haley@gmail.com> wrote:
>
>
> On Tue, Mar 13, 2018 at 6:45 PM, Coda Highland <chighland@gmail.com> wrote:
>>
>> On Tue, Mar 13, 2018 at 7:47 PM, Tomás Guisasola
>> <tomas@tecgraf.puc-rio.br> wrote:
>> > Hi Roberto
>> >
>> >> No, this is not like _javascript_! 'undef' is NOT a value.
>> >
>> > But it is used as a value. It sounds strange to me...
>> >
>> >>
>> >> t[i]=undef is a special syntax form that means "remove the key 'i'
>> >> from table 't'".
>> >
>> > But it seems like an assignment. Wouldn't be better to create a special
>> > syntax for removing a key from a table instead pretending it as an
>> > assingment?
>> >
>> > You should have considered a pair of functions, such as
>> > table.undefine(t, i)
>> > to undefine a key, and table.defined(t, i) to check whether the table
>> > has
>> > the key. Why did you choose the assignment?
>> >
>> > Regards,
>> > Tomás
>>
>> Functions are a bad idea, because this really is a language primitive.
>
>
> Can I ask why this would be considered a primitive and not just a behaviour
> of tables?
> If it were a function it could be re-assigned and used as a check for any
> bounds value or "tomb stone". It would potentially also be valid in both
> normal and LUA_NILINTABLE mode.
>
> Cheers,
> Russ

Given that tables are the fundamental compound data type of Lua,
there's not a whole lot of distinction. I would consider this to be
akin to rawset, which I also consider to be a primitive operation.
Perhaps it could be superficially a function instead of a keyword, but
it's still effectively a language builtin.

/s/ Adam