Cfrgtkky

In TeX, a 'write' node is inserted with, say:

write1{stringdoit{thelastypos}}

With pure luatex, a node could be created with:

local n = node.new(8, 1)

n.stream = 1

n.data = <token-list>

According to the manual, the <token-list> is a table representing the token list to be written (with a list of triplets). I couldn't find any documentation about how this list is built. I discovered a string is accepted, but it gets converted to a string'ed list of chars (much like meaning), so thelastypos is written verbatim, not evaluated.

I've found a workaround, shown in the following piece of code:

setbox0hbox{write1{thelastxpos}}



directlua{



  for _,d in ipairs(tex.box[0].head.data) do

    texio.write(' ** ' .. d[1] .. '/' .. d[2] .. '/' .. d[3])

  end



}

I define a box with a write and then inspect the node. In the real code, instead of printing it I pass it to n.data and primitives work as expected (with some problems in user defined macros).

My question is: how to generate in lua the token list to feed the data field? [Edit. Please, note my questions is not about lastypos, but about building an arbitrary token list for the data field. Remember also that, because of the asynchronous nature of TeX, page numbers and the like are not known when the 'write' node is created, only when the 'write' is actually output.]

Here is a latex file to make some experiments, with a lua file named extra.lua:

documentclass{article}



defdonothing#1{}



directlua{

  require'extra'

}



setbox0hbox{write1{stringdonothing{thelastypos}}}



begin{document}



directlua{



for _,d in ipairs(tex.box[0].head.data) do

  texio.write(' +++ ' .. d[1] .. '/' .. d[2] .. '/' .. d[3])

end



}



copy0

copy0

copy0



end{document}

The lua file:

local n = node.new(8, 1)

n.stream = 1

n.data =  'abcd#&\the\lastxpos' 



for _,d in ipairs(n.data) do

  texio.write(' *** ' .. d[1] .. '/' .. d[2] .. '/' .. d[3])

end

LuaTeX has the token.create function to create a token uservalue. They can be combined into a token list by putting them into a table. For stringdonothing{thelastvpos} this would be:

tl = {

  token.create'string',

  token.create'donothing',

  token.create(string.byte'{'),

    token.create'the',

    token.create'lastypos',

  token.create(string.byte'}')

}

Normally the references to tokenlists in the LuaTeX documentation mean this kind of table, but you need a different kind: A table of tables of numbers. Finding these numbers isn't easy, but you can convert token lists in the format above into this other format (Here I am using a little trick: {0, v.tok} is interpreted in the same way as if we would have split v.tok properly into three parts):

directlua{

local function convert_tl(list)

  local new = {}

  for i,v in ipairs(list) do

    new[i] = {0, v.tok}

  end

  return new

end



local n = node.new(8, 1)

n.stream = 3

n.data = convert_tl{

  token.create'string',

  token.create'donothing',

  token.create(string.byte'{'),

    token.create'the',

    token.create'lastypos',

  token.create(string.byte'}')

}



tex.box[0] = node.hpack(n)

}

copy0

copy0

results in the output

donothing{0}

donothing{0}