[NTG-context] protected macro vs protected luacall

[Hans Hagen]

On 1/27/2023 10:13 AM, Henri Menke via ntg-context wrote:
> On Thu, 2023-01-26 at 23:07 +0100, Hans Hagen via ntg-context wrote:
>> On 1/26/2023 9:33 PM, Henri Menke via ntg-context wrote:
>>> \directlua{
>>>     userdata = userdata or {}
>>>     function userdata.test()
>>>       tex.print("\string\\numexpr 17\string\\relax")
>>>     end
>>> }
>>>
>>> \tt
>>> \protected\def\test{\directlua{userdata.test()}}
>>> \meaning\test\par
>>> \edef\x{\test}\meaning\x\par
>>> \the\test
>>>
>>> \directlua{
>>>     local t = lua.get_functions_table()
>>>     t[\string#t + 1] = userdata.test
>>>     token.set_lua("test", userdata.test, \string#t, "protected")
>>> }
>>> \meaning\test\par
>>> \edef\x{\test}\meaning\x\par
>>> \the\test
>> from the code it looks like we're talking plain luatex ...
>>
>> \the is very selective and doesn't work for all primitives or macros
>>
>> compare it to \number which accepts any number representation
>> following
>> it while \the doesn't work ok 123
>>
>> that said, your set_lua is wrong and passes a function as well as an
>> index
>>
>> \directlua{
>>      lua.get_functions_table()[999] = function()
>>        tex.print("\string\\numexpr 17\string\\relax")
>>      end
>>      token.set_lua("test", 999)
>> }
>>
>> \the    \test % needs the \numexpr
>>
>> \number \test % doesn't
>>
>> \count0 \test % needs the \numexpr
>>
>> \count0=\test % doesn't
>>
>> etc
> 
> Thanks for pointing out my mistake. Your example works fine but now the
> luacall is no longer protected and will therefore fully expand in
> \edef. So do I understand this correctly that there is no way to make
> the second \the\test work?
>
> \directlua{
>      lua.get_functions_table()[999] = function()
>        tex.pri
> nt("\string\\numexpr 17\string\\relax")
>      end
> }
> 
> \tt
> \directlua{token.set_lua("test", 999)}
> \meaning\test\par % expandable luacall 999
> \edef\x{\test}\meaning\x\par % macro:->\numexpr 17\relax
> \the\test % 17
> 
> \directlua{token.set_lua("test", 999, "protected")}
> \meaning\test\par % luacall 999
> \edef\x{\test}\meaning\x\par % macro:->\test
> \the\test % ! You can't use `luacall 999' after \the.
> 
> \bye
you can do

\directlua{
    function TestCmd()
      tex.print("\string\\numexpr 17\string\\relax")
    end
}

\protected\def\test{\directlua{TestCmd()}}

or, more efficient:

\directlua{
    function TestCmd()
      tex.print("17")
    end
}

\protected\def\test{\numexpr\directlua{TestCmd()}\relax}

Hans

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