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In providing an answer to my recent post "Preserving spaces when scanning tl variables into a sequence using seq_set_split" Enrico Gregorio defined __rn_add:n to be called by tl_map_function. In experimenting with tl_map_ and seq_map_functions it occurred to me that the possibility of defining such functions having more than just one argument would be useful; for example __rn_add:nN might use #1 for the tl item and have #2 specify to which _seq variable to add the item. I assume the _function versions of tl_map and seq_map were intended to define processes for general use, while the _inline versions provide greatest flexibility but need to be written anew for each tl_map_ and seq_map_inline, or am I completely off the mark here?

documentclass{article}

usepackage[margin=1cm]{geometry}

usepackage{xparse}



ExplSyntaxOn

tl_new:N l_rn_auxOne_tl

tl_new:N l_rn_auxTwo_tl

seq_new:N l_rn_auxOne_seq

seq_new:N l_rn_auxTwo_seq



NewDocumentCommandmyScanText{m}

 {

  tl_set:Nn l_rn_auxOne_tl {#1}

  seq_clear:N l_rn_auxOne_seq

  % split at spaces

  seq_set_split:Nnn l_rn_auxTwo_seq {~} { #1 }

  % the first item is special, pop it out and split it

  seq_pop_left:NN l_rn_auxTwo_seq l_rn_auxTwo_tl

  tl_map_function:NN l_rn_auxTwo_tl __rn_add:n

  % now do the other items, reinserting the space before them

  seq_map_inline:Nn l_rn_auxTwo_seq

   {

    __rn_add:n { ~ }

    tl_map_function:nN { ##1 } __rn_add:n

   }

  % print the data

  textbf{tl~variable:}~tl_use:N l_rn_auxOne_tl\

  textbf{seq~variable:}~seq_use:Nn l_rn_auxOne_seq {,}

 }

cs_new_protected:Nn __rn_add:n

 {

  seq_put_right:Nn l_rn_auxOne_seq { #1 }

 }

ExplSyntaxOff

%-----------------------

begin{document}



setlength{parindent}{0pt} % just for the example



myScanText{The quick brown fox jumps over the lazy dog.}



end{document}

If you need the expandability in a certain point, you can do

cs_set:Npn __rn_add:n #1 { rn_macro_with_two_args:nN { #1 } l_rn_addto_seq }

% ^ this before where you can, and then  v this in an expandable context

tl_map_function:NN l_rn_auxii_tl __rn_add:n

But if you don't need expandability you can always do the inline version:

seq_map_inline:Nn l_rn_auxii_seq

 {

  __rn_add:n { ~ }

  tl_map_inline:nn { ##1 }

   {

    rn_macro_with_two_args:nN { ###1 } l_rn_addto_seq

   }

 }