On 10/16/2021 10:33 AM, Wolfgang Schuster via ntg-context wrote:
> Ramkumar KB via ntg-context schrieb am 16.10.2021 um 06:00:
>> Hello All,
>>
>> I was trying to read the value of '\totalnumberofpages' into lua to do
>> something with it. As an example, see below.
>>
>> Now, as I understand it, my example would not work as TeX gets the
>> first go at this and therefore the variable 'pages' is the string
>> '\totalnumberofpages' and not the actual value itself. And Lua cannot
>> process this "calculation".
>>
>> I tried to go thru the manual - *cld-mkiv.pdf *- in the distro but
>> could not catch on how to read a metadata value (not print). I am sure
>> that I am missing a small trick somewhere (or is it something more
>> involved?).
>>
>> \startluacode
>> function myFancyCalculations(pages)
>>   -- some fancy stuff but as an example
>> local myCal = tonumber(pages) + 1
>> return myCal
>> \stopluacode
>> \starttext
>>
>> \blah
>>
>> \ctxlua{context(myFancyCalculations("\\totalnumberofpages"))}
>>
>> \stoptext
>
> Everything gets easier when you use the Lua functions to access the
> counter values but be aware the values can be wrong when you're at a
> page break.
>
> \startbuffer[pagenumber]
> \startluacode
> context.starttabulate()
>      context.NC()
>          context("Current page")
>      context.EQ()
>          context(structures.counters.get("realpage",1,"number"))
>      context.NC()
>      context.NR()
>      context.NC()
>          context("Last page")
>      context.EQ()
>          context(structures.counters.get("realpage",1,"last"))
>      context.NC()
>      context.NR()
> context.stoptabulate()
> \stopluacode
> \stopbuffer
>
> \starttext
>
> \dorecurse
>      {\randomnumber{5}{10}}
>      {\getbuffer[pagenumber]
>       \page}
>
> \stoptext

As addendum ... The problem in general with macros is that one doesn't
really knows by looking at the name what actually happens when it
expands, which can be a lot. Now, because \totalnumberofpages is
supposed to 'return' a number and not typeset something styled (which
itself involved macro expansion) you can actually do this:

\startluacode
local n = tokens.getters.macro("totalnumberofpages",true)
print(">>>",type(n),n)
\stopluacode

but beware of the fact that you actually get back a string:

\startluacode
local n = tokens.getters.macro("totalnumberofpages",true)
print(">>>",type(n),n)
local n = tonumber(n)
print(">>>",type(n),n)
\stopluacode

etc etc

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@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________