[NTG-context] protected macro vs protected luacall

[Henri Menke]

On Fri, 2023-01-27 at 10:30 +0100, Hans Hagen via ntg-context wrote:
> 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}

Thanks, this is indeed the workaround that I currently use. However,
the downside is that this has to tokenize the contents of \directlua
every time (and is therefore susceptible to surrounding \catcode
shenanigans) and it expands in at minimum two steps, whereas a luacall
always expands in a single step. But I guess that's what I will have to
live with.

Cheers, Henri

> 
> Hans
> 
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
> -----------------------------------------------------------------
> 
> _____________________________________________________________________
> ______________
> If your question is of interest to others as well, please add an
> entry to the Wiki!
> 
> maillist : ntg-context at ntg.nl / 
> https://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : https://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : https://contextgarden.net
> _____________________________________________________________________
> ______________