brdcrmbs/lt3wstack.sty at master · vermiculus/brdcrmbs · GitHub

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\RequirePackage{expl3}[2014/11/25]
\ProvidesExplPackage
  {lt3wstack}
  {2015/03/01}
  {0.1}
  {a weighted-stack data-structure for expl3}

%% The weighted stack is just a stack that associates nodes with
%% weights (or priorities, depending on how you look at it).  When a
%% node is pushed onto the stack, it will pop all those nodes with a
%% weight greater than or equal to its own.

% \wstack_new:N :: create new stack
% \wstack_show:N :: output data to terminal (no weights yet)
% \wstack_use:Nn(nn)? :: interface to \seq_use:Nn(nn)?
% \wstack_g?push:Nnn :: (globally)? push #3 to #1 with weight=#2
% \wstack_g?pop_to:Nn :: (globally)? pop #1 down past weight #2
% \wstack_g?clear:N :: (globally)? clear content of stack

% @todo
%
% The weighted stack \test_wstack contains the items (without outer braces):
% >  (200) {hello-200}
% >  ( 12) {hello-12}
% >  (  2) {hello-2}
% >  (  1) {hello-1}.
% <recently read> }
%
% l.??? \wstack_show:N \test_wstack

\cs_gset_eq:NN \wstack_new:N    \seq_new:N
\cs_gset_eq:NN \wstack_use:Nn   \seq_use:Nn
\cs_gset_eq:NN \wstack_use:Nnnn \seq_use:Nnnn
\cs_gset_eq:NN \wstack_show:N   \seq_show:N
\cs_gset_eq:NN \wstack_clear:N  \seq_clear:N
\cs_gset_eq:NN \wstack_gclear:N \seq_gclear:N

\cs_new:Npn \wstack_gpush:Nnn #1 #2 #3 {
  \wstack_push:Nnn #1 {#2} {#3}
  \seq_gset_eq:NN #1 #1
}
\cs_new:Npn \wstack_push:Nnn #1 #2 #3 {
  \wstack_pop_to:Nn #1 {#2}
  \seq_clear:N \l_tmpa_seq
  \seq_push:Nn \l_tmpa_seq {#3}
  \seq_push:Nn \l_tmpa_seq {#2}
  \seq_push:NV #1 \l_tmpa_seq
}

\cs_new:Npn \wstack_gpop_to:Nn #1 #2 {
  \wstack_pop_to:Nn #1 {#2}
  \seq_gset_eq:NN #1 #1
}
\cs_new:Npn \wstack_pop_to:Nn #1 #2 {
  \seq_get:NN #1 \l_tmpa_seq
  \seq_get:NN \l_tmpa_seq \l_tmpa_tl
  \bool_until_do:nn {
    \quark_if_no_value_p:N \l_tmpa_tl ||
    \int_compare_p:nNn {#2} > \l_tmpa_tl
  }
  {
    \seq_pop:NN #1 \l_tmpa_seq
    \seq_get:NN #1 \l_tmpa_seq
    \seq_get:NN \l_tmpa_seq \l_tmpa_tl
  }
}

%  Tests

 \wstack_new:N     \test_wstack
 \wstack_push:Nnn  \test_wstack 1 {one}
 \wstack_push:Nnn  \test_wstack 2 {two}
 \wstack_push:Nnn  \test_wstack 3 {three}
 \wstack_push:Nnn  \test_wstack 4 {four}
 \wstack_show:N    \test_wstack  % 4321

 \wstack_push:Nnn  \test_wstack 2 {two-b}
 \wstack_show:N    \test_wstack  % 21
 \wstack_push:Nnn  \test_wstack 8 {EIGHT}
 \wstack_show:N    \test_wstack  % 821
{\wstack_gpush:Nnn \test_wstack 2 {two-c}}
 \wstack_show:N    \test_wstack  % 21
 \wstack_push:Nnn  \test_wstack {-1} {the basest}
 \wstack_show:N    \test_wstack  % -1

% to test, run `latex lt3wstack.sty'
\tex_end:D