% This is etex.ch in text format, as of January 31, 1999.
% WEB change file containing code for various features extending TeX;
% to be applied to tex.web (Version 3.14159) in order to define the
% e-TeX program.

% e-TeX is copyright (C) 1994,98 by the NTS team; all rights are reserved.
% Copying of this file is authorized only if (1) you are a member of the
% NTS team, or if (2) you make absolutely no changes to your copy.
% (Programs such as PATCHWEB, TIE, or WEBMERGE allow the application of
% several change files to tex.web; the master files tex.web and etex.ch
% should stay intact.)

% See etex_gen.tex for hints on how to install this program.
% And see etripman.tex for details about how to validate it.

% The TeX program is copyright (C) 1982 by D. E. Knuth.
% TeX is a trademark of the American Mathematical Society.
% e-TeX and NTS are trademarks of the NTS group.

% All line numbers refer to TEX.WEB 3.14159 as of March 21, 1995.

@x limbo l.1 - this is e-TeX
% This program is copyright (C) 1982 by D. E. Knuth; all rights are reserved.
% Copying of this file is authorized only if (1) you are D. E. Knuth, or if
% (2) you make absolutely no changes to your copy. (The WEB system provides
% for alterations via an auxiliary file; the master file should stay intact.)
% See Appendix H of the WEB manual for hints on how to install this program.
% And see Appendix A of the TRIP manual for details about how to validate it.

% TeX is a trademark of the American Mathematical Society.
% METAFONT is a trademark of Addison-Wesley Publishing Company.
@y
% e-TeX is copyright (C) 1994,98 by the NTS team; all rights are reserved.
% Copying of this file is authorized only if (1) you are a member of the
% NTS team, or if (2) you make absolutely no changes to your copy.
% (Programs such as PATCHWEB, TIE, or WEBMERGE allow the application of
% several change files to tex.web; the master files tex.web and etex.ch
% should stay intact.)

% See etex_gen.tex for hints on how to install this program.
% And see etripman.tex for details about how to validate it.

% e-TeX and NTS are trademarks of the NTS group.
% TeX is a trademark of the American Mathematical Society.
% METAFONT is a trademark of Addison-Wesley Publishing Company.

% This program is directly derived from Donald E. Knuth's TeX;
% the change history which follows and the reward offered for finders of
% bugs refer specifically to TeX; they should not be taken as referring
% to e-TeX, although the change history is relevant in that it
% demonstrates the evolutionary path followed.  This program is not TeX;
% that name is reserved strictly for the program which is the creation
% and sole responsibility of Professor Knuth.
@z
%---------------------------------------
@x limbo l.50 - e-TeX history
% Although considerable effort has been expended to make the TeX program
% correct and reliable, no warranty is implied; the author disclaims any
% obligation or liability for damages, including but not limited to
% special, indirect, or consequential damages arising out of or in
% connection with the use or performance of this software. This work has
% been a ``labor of love'' and the author hopes that users enjoy it.
@y
% A preliminary version of TeX--XeT was released in April 1992.
% TeX--XeT version 1.0 was released in June 1992,
%   version 1.1 prevented arith overflow in glue computation (Oct 1992).
% A preliminary e-TeX version 0.95 was operational in March 1994.
% Version 1.0beta was released in May 1995.
% Version 1.01beta fixed bugs in just_copy and every_eof (December 1995).
% Version 1.02beta allowed 256 mark classes (March 1996).
% Version 1.1 changed \group{type,level} -> \currentgroup{type,level},
%             first public release (October 1996).
% Version 2.0 development was started in March 1997;
%             fixed a ligature-\beginR bug in January 1998;
%             was released in March 1998.
% Version 2.1 fixed a marks bug (when min_halfword<>0) (January 1999).

% Although considerable effort has been expended to make the e-TeX program
% correct and reliable, no warranty is implied; the authors disclaim any
% obligation or liability for damages, including but not limited to
% special, indirect, or consequential damages arising out of or in
% connection with the use or performance of this software. This work has
% been a ``labor of love'' and the authors hope that users enjoy it.
@z
%---------------------------------------
@x limbo l.61 - e-TeX logo, TeXXeT
\let\mc=\ninerm % medium caps for names like SAIL
@y
\let\mc=\ninerm % medium caps for names like SAIL
\def\eTeX{$\varepsilon$-\TeX}
\font\revrm=xbmc10 % for right-to-left text
% to generate xbmc10 (i.e., reflected cmbx10) use a file
% xbmc10.mf containing:
%+++++++++++++++++++++++++++++++++++++++++++++++++
%     if unknown cmbase: input cmbase fi
%     extra_endchar := extra_endchar &
%       "currentpicture:=currentpicture " &
%       "reflectedabout((.5[l,r],0),(.5[l,r],1));";
%     input cmbx10
%+++++++++++++++++++++++++++++++++++++++++++++++++
\ifx\beginL\undefined % this is TeX
  \def\XeT{X\kern-.125em\lower.5ex\hbox{E}\kern-.1667emT}
  \def\TeXeT{\TeX-\hbox{\revrm \XeT}}   % for TeX-XeT
  \def\TeXXeT{\TeX-\hbox{\revrm -\XeT}} % for TeX--XeT
\else
  \ifx\eTeXversion\undefined % this is \TeXeT
    \def\TeXeT{\TeX-{\revrm\beginR\TeX\endR}}   % for TeX-XeT
    \def\TeXXeT{\TeX-{\revrm\beginR\TeX-\endR}} % for TeX--XeT
  \else % this is \eTeX
    \def\TeXeT{\TeX-{\TeXXeTstate=1\revrm\beginR\TeX\endR}}   % for TeX-XeT
    \def\TeXXeT{\TeX-{\TeXXeTstate=1\revrm\beginR\TeX-\endR}} % for TeX--XeT
  \fi
\fi
@z
%---------------------------------------
@x limbo l.64 - bug fix (print only changed modules)
\def\pct!{{\char`\%}} % percent sign in ordinary text
@y
\def\pct!{{\char`\%}} % percent sign in ordinary text
\def\grp{\.{\char'173...\char'175}}
@z
%---------------------------------------
@x limbo l.80 - e-TeX basic
\def\title{\TeX82}
@y
\def\title{\eTeX}
% system dependent redefinitions of \title should come later
% and should use:
%    \toks0=\expandafter{\title}
%    \edef\title{...\the\toks0...}
\let\maybe=\iffalse % print only changed modules
@z
%---------------------------------------
@x [1] m.1 l.91 - this is e-TeX
This is \TeX, a document compiler intended to produce typesetting of high
@y
This is \eTeX, a program derived from and extending the capabilities of
\TeX, a document compiler intended to produce typesetting of high
@z
%---------------------------------------
@x [1] m.2 l.179 - e-TeX basic
If this program is changed, the resulting system should not be called
@y
This program contains code for various features extending \TeX,
therefore this program is called `\eTeX' and not
@z
%---------------------------------------
@x [1] m.2 l.185 - e-TeX basic
November 1984].
@y
November 1984].

A similar test suite called the ``\.{e-TRIP} test'' is available for
helping to determine whether a particular implementation deserves to be
known as `\eTeX'.
@z
%---------------------------------------
@x [1] m.2 l.187 - e-TeX basic
@d banner=='This is TeX, Version 3.14159' {printed when \TeX\ starts}
@y
@d banner=='This is TeX, Version 3.14159' {printed when \TeX\ starts}
@#
@d eTeX_version_string=='3.14159-2.1' {current \eTeX\ version}
@d eTeX_version=2 { \.{\\eTeXversion} }
@d eTeX_revision==".1" { \.{\\eTeXrevision} }
@#
@d eTeX_banner=='This is e-TeX, Version ',eTeX_version_string
  {printed when \eTeX\ starts}
@#
@d TEX==ETEX {change program name into |ETEX|}
@#
@d TeXXeT_code=0 {the \TeXXeT\ feature is optional}
@#
@d eTeX_states=1 {number of \eTeX\ state variables in |eqtb|}
@z
%---------------------------------------
@x [1] m.15 l.493 - e-TeX basic
@d not_found=45 {go here when you've found nothing}
@y
@d not_found=45 {go here when you've found nothing}
@d not_found1=46 {like |not_found|, when there's more than one}
@d not_found2=47 {like |not_found|, when there's more than two}
@d not_found3=48 {like |not_found|, when there's more than three}
@d not_found4=49 {like |not_found|, when there's more than four}
@z
%---------------------------------------
@x [5] m.61 l.1556 - e-TeX basic
wterm(banner);
@y
wterm(eTeX_banner);
@z
%---------------------------------------
@x [10] m.141 l.2965 - e-TeX marks
This field occupies a full word instead of a halfword, because
there's nothing to put in the other halfword; it is easier in \PASCAL\ to
use the full word than to risk leaving garbage in the unused half.
@y
In addition there is a |mark_class| field that contains the mark class.
@z
%---------------------------------------
@x [10] m.141 l.2971 - e-TeX marks
@d mark_ptr(#)==mem[#+1].int {head of the token list for a mark}
@y
@d mark_ptr(#)==link(#+1) {head of the token list for a mark}
@d mark_class(#)==info(#+1) {the mark class}
@z
%---------------------------------------
@x [10] m.142 l.2980 - e-TeX marks
@d adjust_ptr==mark_ptr {vertical list to be moved out of horizontal list}
@y
@d adjust_ptr(#)==mem[#+1].int
  {vertical list to be moved out of horizontal list}
@z
%---------------------------------------
@x [10] m.147 l.3069 - e-TeX TeXXeT
the amount of surrounding space inserted by \.{\\mathsurround}.
@y
the amount of surrounding space inserted by \.{\\mathsurround}.

In addition a |math_node| with |subtype>after| and |width=0| will be
(ab)used to record a regular |math_node| reinserted after being
discarded at a line break or one of the text direction primitives (
\.{\\beginL}, \.{\\endL}, \.{\\beginR}, and \.{\\endR} ).
@z
%---------------------------------------
@x [10] m.147 l.3073 - e-TeX TeXXeT
@d after=1 {|subtype| for math node that winds up a formula}
@y
@d after=1 {|subtype| for math node that winds up a formula}
@#
@d M_code=2
@d begin_M_code=M_code+before {|subtype| for \.{\\beginM} node}
@d end_M_code=M_code+after {|subtype| for \.{\\endM} node}
@d L_code=4
@d begin_L_code=L_code+begin_M_code {|subtype| for \.{\\beginL} node}
@d end_L_code=L_code+end_M_code {|subtype| for \.{\\endL} node}
@d R_code=L_code+L_code
@d begin_R_code=R_code+begin_M_code {|subtype| for \.{\\beginR} node}
@d end_R_code=R_code+end_M_code {|subtype| for \.{\\endR} node}
@#
@d end_LR(#)==odd(subtype(#))
@d end_LR_type(#)==(L_code*(subtype(#) div L_code)+end_M_code)
@d begin_LR_type(#)==(#-after+before)
@z
%---------------------------------------
@x [12] m.175 l.3546 - e-TeX TeXXeT
math_node: print_char("$");
@y
math_node: if subtype(p)>=L_code then print("[]")
  else print_char("$");
@z
%---------------------------------------
@x [12] m.184 l.3713 - e-TeX TeXXeT
    begin print(", shifted "); print_scaled(shift_amount(p));
    end;
@y
    begin print(", shifted "); print_scaled(shift_amount(p));
    end;
  if eTeX_ex then @<Display if this box is never to be reversed@>;
@z
%---------------------------------------
@x [12] m.192 l.3811 - e-TeX TeXXeT
begin print_esc("math");
@y
if subtype(p)>after then
  begin if end_LR(p) then print_esc("end")
  else print_esc("begin");
  if subtype(p)>R_code then print_char("R")
  else if subtype(p)>L_code then print_char("L")
  else print_char("M");
  end else
begin print_esc("math");
@z
%---------------------------------------
@x [12] m.196 l.3844 - e-TeX marks
begin print_esc("mark"); print_mark(mark_ptr(p));
@y
begin print_esc("mark");
if mark_class(p)<>0 then
  begin print_char("s"); print_int(mark_class(p));
  end;
print_mark(mark_ptr(p));
@z
%---------------------------------------
@x [15] m.208 l.4081 - e-TeX saved_items
@d un_vbox=24 {unglue a box ( \.{\\unvbox}, \.{\\unvcopy} )}
@y
@d un_vbox=24 {unglue a box ( \.{\\unvbox}, \.{\\unvcopy} )}
  {( or \.{\\pagediscards}, \.{\\splitdiscards} )}
@z
%---------------------------------------
@x [15] m.208 l.4091 - e-TeX TeXXeT
@d valign=33 {vertical table alignment ( \.{\\valign} )}
@y
@d valign=33 {vertical table alignment ( \.{\\valign} )}
  {or text direction directives ( \.{\\beginL}, etc.~)}
@z
%---------------------------------------
@x [15] m.208 l.4107 - e-TeX middle
@d left_right=49 {variable delimiter ( \.{\\left}, \.{\\right} )}
@y
@d left_right=49 {variable delimiter ( \.{\\left}, \.{\\right} )}
  {( or \.{\\middle} )}
@z
%---------------------------------------
@x [15] m.209 l.4151 - e-TeX basic
  \.{\\insertpenalties} )}
@y
  \.{\\insertpenalties} )}
  {( or \.{\\interactionmode} )}
@z
%---------------------------------------
@x [15] m.209 l.4153 - e-TeX penalties
@d set_shape=84 {specify fancy paragraph shape ( \.{\\parshape} )}
@y
@d set_shape=84 {specify fancy paragraph shape ( \.{\\parshape} )}
  {(or \.{\\interlinepenalties}, etc.~)}
@z
%---------------------------------------
@x [15] m.209 l.4163 - e-TeX protected
@d prefix=93 {qualify a definition ( \.{\\global}, \.{\\long}, \.{\\outer} )}
@y
@d prefix=93 {qualify a definition ( \.{\\global}, \.{\\long}, \.{\\outer} )}
  {( or \.{\\protected} )}
@z
%---------------------------------------
@x [15] m.209 l.4166 - e-TeX read_line
@d read_to_cs=96 {read into a control sequence ( \.{\\read} )}
@y
@d read_to_cs=96 {read into a control sequence ( \.{\\read} )}
  {( or \.{\\readline} )}
@z
%---------------------------------------
@x [15] m.210 l.4181 - e-TeX scan_tokens
@d input=max_command+4 {input a source file ( \.{\\input}, \.{\\endinput} )}
@y
@d input=max_command+4 {input a source file ( \.{\\input}, \.{\\endinput} )}
  {( or \.{\\scantokens} )}
@z
%---------------------------------------
@x [15] m.210 l.4186 - e-TeX unexpanded
@d the=max_command+9 {expand an internal quantity ( \.{\\the} )}
@y
@d the=max_command+9 {expand an internal quantity ( \.{\\the} )}
  {( or \.{\\unexpanded}, \.{\\detokenize} )}
@z
%---------------------------------------
@x [16] m.212 l.4289 - e-TeX basic
user's output routine.
@y
user's output routine.

A seventh quantity, |eTeX_aux|, is used by the extended features \eTeX.
In vertical modes it is known as |LR_save| and holds the LR stack when a
paragraph is interrupted by a displayed formula.  In display math mode
it is known as |LR_box| and holds a pointer to a prototype box for the
display.  In math mode it is known as |delim_ptr| and points to the most
recent |left_noad| or |middle_noad| of a |math_left_group|.
@z
%---------------------------------------
@x [16] m.212 l.4304 - e-TeX basic
  @!head_field,@!tail_field: pointer;
@y
  @!head_field,@!tail_field: pointer;
  @!eTeX_aux_field: pointer;
@z
%---------------------------------------
@x [16] m.213 l.4311 - e-TeX basic
@d tail==cur_list.tail_field {final node on current list}
@y
@d tail==cur_list.tail_field {final node on current list}
@d eTeX_aux==cur_list.eTeX_aux_field {auxiliary data for \eTeX}
@d LR_save==eTeX_aux {LR stack when a paragraph is interrupted}
@d LR_box==eTeX_aux {prototype box for display}
@d delim_ptr==eTeX_aux {most recent left or right noad of a math left group}
@z
%---------------------------------------
@x [16] m.215 l.4342 - e-TeX basic
mode:=vmode; head:=contrib_head; tail:=contrib_head;
@y
mode:=vmode; head:=contrib_head; tail:=contrib_head;
eTeX_aux:=null;
@z
%---------------------------------------
@x [16] m.216 l.4358 push_nest - e-TeX basic
incr(nest_ptr); head:=get_avail; tail:=head; prev_graf:=0; mode_line:=line;
@y
incr(nest_ptr); head:=get_avail; tail:=head; prev_graf:=0; mode_line:=line;
eTeX_aux:=null;
@z
%---------------------------------------
@x [17] m.230 l.4712 - e-TeX basic, penalties
@d output_routine_loc=local_base+1 {points to token list for \.{\\output}}
@d every_par_loc=local_base+2 {points to token list for \.{\\everypar}}
@d every_math_loc=local_base+3 {points to token list for \.{\\everymath}}
@d every_display_loc=local_base+4 {points to token list for \.{\\everydisplay}}
@d every_hbox_loc=local_base+5 {points to token list for \.{\\everyhbox}}
@d every_vbox_loc=local_base+6 {points to token list for \.{\\everyvbox}}
@d every_job_loc=local_base+7 {points to token list for \.{\\everyjob}}
@d every_cr_loc=local_base+8 {points to token list for \.{\\everycr}}
@d err_help_loc=local_base+9 {points to token list for \.{\\errhelp}}
@d toks_base=local_base+10 {table of 256 token list registers}
@y
@d inter_line_penalties_loc=local_base+1 {additional penalties between lines}
@d club_penalties_loc=local_base+2 {penalties for creating club lines}
@d widow_penalties_loc=local_base+3 {penalties for creating widow lines}
@d display_widow_penalties_loc=local_base+4 {ditto, just before a display}
@d token_base=local_base+5 {table of token list parameters}
@d output_routine_loc=token_base {points to token list for \.{\\output}}
@d every_par_loc=token_base+1 {points to token list for \.{\\everypar}}
@d every_math_loc=token_base+2 {points to token list for \.{\\everymath}}
@d every_display_loc=token_base+3 {points to token list for \.{\\everydisplay}}
@d every_hbox_loc=token_base+4 {points to token list for \.{\\everyhbox}}
@d every_vbox_loc=token_base+5 {points to token list for \.{\\everyvbox}}
@d every_job_loc=token_base+6 {points to token list for \.{\\everyjob}}
@d every_cr_loc=token_base+7 {points to token list for \.{\\everycr}}
@d every_eof_loc=token_base+8 {points to token list for \.{\\everyeof}}
@d err_help_loc=token_base+9 {points to token list for \.{\\errhelp}}
@d toks_base=token_base+10 {table of 256 token list registers}
@z
%---------------------------------------
@x [17] m.231 l.4787 - e-TeX basic
  othercases print_esc("errhelp")
@y
  @/@<Cases of |assign_toks| for |print_cmd_chr|@>@/
  othercases print_esc("errhelp")
@z
%---------------------------------------
@x [17] m.232 l.4805 - e-TeX penalties
eq_level(par_shape_loc):=level_one;@/
@y
eq_level(par_shape_loc):=level_one;@/
for k:=par_shape_loc+1 to token_base-1 do
  eqtb[k]:=eqtb[par_shape_loc];
@z
%---------------------------------------
@x [17] m.233 l.4833 - e-TeX penalties
if n=par_shape_loc then
  begin print_esc("parshape"); print_char("=");
  if par_shape_ptr=null then print_char("0")
  else print_int(info(par_shape_ptr));
@y
if n<token_base then
  begin print_cmd_chr(set_shape,n); print_char("=");
  if equiv(n)=null then print_char("0")
  else if n>par_shape_loc then
    begin print_int(penalty(equiv(n))); print_char(" ");
    print_int(penalty(equiv(n)+1));
    if penalty(equiv(n))>1 then print_esc("ETC.");
    end
  else print_int(info(par_shape_ptr));
@z
%---------------------------------------
@x [17] m.236 l.4955 - e-TeX basic
@d count_base=int_base+int_pars {256 user \.{\\count} registers}
@y
@d tracing_assigns_code=int_pars {show assignments}
@d tracing_groups_code=int_pars+1 {show save/restore groups}
@d tracing_ifs_code=int_pars+2 {show conditionals}
@d tracing_scan_tokens_code=int_pars+3 {show pseudo file open and close}
@d tracing_nesting_code=int_pars+4
  {show incomplete groups and ifs within files}
@d pre_display_direction_code=int_pars+5 {text direction preceding a display}
@d last_line_fit_code=int_pars+6 {adjustment for last line of paragraph}
@d saving_vdiscards_code=int_pars+7 {save items discarded from vlists}
@d saving_hyph_codes_code=int_pars+8 {save hyphenation codes for languages}
@d eTeX_state_code=int_pars+9 {\eTeX\ state variables}
@d count_base=int_base+eTeX_state_code+eTeX_states
  {256 user \.{\\count} registers}
@z
%---------------------------------------
@x [17] m.236 l.5016 - e-TeX basic
@d error_context_lines==int_par(error_context_lines_code)
@y
@d error_context_lines==int_par(error_context_lines_code)
@d tracing_assigns==int_par(tracing_assigns_code)
@d tracing_groups==int_par(tracing_groups_code)
@d tracing_ifs==int_par(tracing_ifs_code)
@d tracing_scan_tokens==int_par(tracing_scan_tokens_code)
@d tracing_nesting==int_par(tracing_nesting_code)
@d pre_display_direction==int_par(pre_display_direction_code)
@d last_line_fit==int_par(last_line_fit_code)
@d saving_vdiscards==int_par(saving_vdiscards_code)
@d saving_hyph_codes==int_par(saving_hyph_codes_code)
@z
%---------------------------------------
@x [17] m.237 l.5081 print_param - e-TeX basic
othercases print("[unknown integer parameter!]")
@y
@/@<Cases for |print_param|@>@/
othercases print("[unknown integer parameter!]")
@z
%---------------------------------------
@x [18] m.264 l.5612 primitive - e-TeX basic
@!j:small_number; {index into |buffer|}
@y
@!j:0..buf_size; {index into |buffer|}
@z
%---------------------------------------
@x [18] m.264 l.5616 primitive - e-TeX basic
    {we will move |s| into the (empty) |buffer|}
  for j:=0 to l-1 do buffer[j]:=so(str_pool[k+j]);
  cur_val:=id_lookup(0,l); {|no_new_control_sequence| is |false|}
@y
    {we will move |s| into the (possibly non-empty) |buffer|}
  if first+l>buf_size+1 then
      overflow("buffer size",buf_size);
@:TeX capacity exceeded buffer size}{\quad buffer size@>
  for j:=0 to l-1 do buffer[first+j]:=so(str_pool[k+j]);
  cur_val:=id_lookup(first,l); {|no_new_control_sequence| is |false|}
@z
%---------------------------------------
@x [18] m.265 l.5691 - e-TeX penalties
primitive("parshape",set_shape,0);@/
@y
primitive("parshape",set_shape,par_shape_loc);@/
@z
%---------------------------------------
@x [18] m.265 l.5708 - e-TeX sparse arrays
primitive("toks",toks_register,0);@/
@y
primitive("toks",toks_register,mem_bot);@/
@z
%---------------------------------------
@x [18] m.266 l.5741 - e-TeX cond
expand_after: print_esc("expandafter");
@y
expand_after: if chr_code=0 then print_esc("expandafter")
  @<Cases of |expandafter| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [18] m.266 l.5747 - e-TeX marks
mark: print_esc("mark");
@y
mark: begin print_esc("mark");
  if chr_code>0 then print_char("s");
  end;
@z
%---------------------------------------
@x [18] m.266 l.5758 - e-TeX read_line
read_to_cs: print_esc("read");
@y
read_to_cs: if chr_code=0 then print_esc("read")
  @<Cases of |read| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [18] m.266 l.5762 - e-TeX penalties
set_shape: print_esc("parshape");
@y
set_shape: case chr_code of
  par_shape_loc: print_esc("parshape");
  @<Cases of |set_shape| for |print_cmd_chr|@>@;@/
  end; {there are no other cases}
@z
%---------------------------------------
@x [18] m.266 l.5763 - e-TeX unexpanded
the: print_esc("the");
@y
the: if chr_code=0 then print_esc("the")
  @<Cases of |the| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [18] m.266 l.5764 - e-TeX sparse arrays
toks_register: print_esc("toks");
@y
toks_register: @<Cases of |toks_register| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [18] m.266 l.5766 - e-TeX TeXXeT
valign: print_esc("valign");
@y
valign: if chr_code=0 then print_esc("valign")@/
  @<Cases of |valign| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [19] m.268 l.5800 - e-TeX sparse arrays
interpreted in one of four ways:
@y
interpreted in one of five ways:
@z
%---------------------------------------
@x [19] m.268 l.5820 - e-TeX tracing
the entries for that group.
@y
the entries for that group.
Furthermore, in extended \eTeX\ mode, |save_stack[p-1]| contains the
source line number at which the current level of grouping was entered.

\yskip\hang 5) If |save_type(p)=restore_sa|, then |sa_chain| points to a
chain of sparse array entries to be restored at the end of the current
group. Furthermore |save_index(p)| and |save_level(p)| should replace
the values of |sa_chain| and |sa_level| respectively.
@z
%---------------------------------------
@x [19] m.268 l.5830 - e-TeX basic
@d level_boundary=3 {|save_type| corresponding to beginning of group}
@y
@d level_boundary=3 {|save_type| corresponding to beginning of group}
@d restore_sa=4 {|save_type| when sparse array entries should be restored}

@p@t\4@>@<Declare \eTeX\ procedures for tracing and input@>
@z
%---------------------------------------
@x [19] m.273 l.5888 - e-TeX tracing
@ The following macro is used to test if there is room for up to six more
@y
@ The following macro is used to test if there is room for up to seven more
@z
%---------------------------------------
@x [19] m.273 l.5894 check_full_save_stack - e-TeX tracing
  if max_save_stack>save_size-6 then overflow("save size",save_size);
@y
  if max_save_stack>save_size-7 then overflow("save size",save_size);
@z
%---------------------------------------
@x [19] m.274 l.5916 new_save_level - e-TeX tracing
begin check_full_save_stack;
@y
begin check_full_save_stack;
if eTeX_ex then
  begin saved(0):=line; incr(save_ptr);
  end;
@z
%---------------------------------------
@x [19] m.274 l.5923 new_save_level - e-TeX tracing
cur_boundary:=save_ptr; incr(cur_level); incr(save_ptr); cur_group:=c;
@y
cur_boundary:=save_ptr; cur_group:=c;
@!stat if tracing_groups>0 then group_trace(false);@+tats@;@/
incr(cur_level); incr(save_ptr);
@z
%---------------------------------------
@x [19] m.275 l.5941 eq_destroy - e-TeX sparse arrays
othercases do_nothing
@y
@/@<Cases for |eq_destroy|@>@/
othercases do_nothing
@z
%---------------------------------------
@x [19] m.277 l.5963 - e-TeX tracing
the call, since |eq_save| makes the necessary test.
@y
the call, since |eq_save| makes the necessary test.

@d assign_trace(#)==@!stat if tracing_assigns>0 then restore_trace(#);
  tats
@z
%---------------------------------------
@x [19] m.277 l.5967 eq_define - e-TeX tracing
begin if eq_level(p)=cur_level then eq_destroy(eqtb[p])
@y
label exit;
begin if eTeX_ex and(eq_type(p)=t)and(equiv(p)=e) then
  begin assign_trace(p,"reassigning")@;@/
  eq_destroy(eqtb[p]); return;
  end;
assign_trace(p,"changing")@;@/
if eq_level(p)=cur_level then eq_destroy(eqtb[p])
@z
%---------------------------------------
@x [19] m.277 l.5970 eq_define - e-TeX tracing
end;
@y
assign_trace(p,"into")@;@/
exit:end;
@z
%---------------------------------------
@x [19] m.278 l.5977 eq_word_define - e-TeX tracing
begin if xeq_level[p]<>cur_level then
@y
label exit;
begin if eTeX_ex and(eqtb[p].int=w) then
  begin assign_trace(p,"reassigning")@;@/
  return;
  end;
assign_trace(p,"changing")@;@/
if xeq_level[p]<>cur_level then
@z
%---------------------------------------
@x [19] m.278 l.5981 eq_word_define - e-TeX tracing
end;
@y
assign_trace(p,"into")@;@/
exit:end;
@z
%---------------------------------------
@x [19] m.279 l.5990 geq_define - e-TeX tracing
begin eq_destroy(eqtb[p]);
eq_level(p):=level_one; eq_type(p):=t; equiv(p):=e;
@y
begin assign_trace(p,"globally changing")@;@/
begin eq_destroy(eqtb[p]);
eq_level(p):=level_one; eq_type(p):=t; equiv(p):=e;
end;
assign_trace(p,"into")@;@/
@z
%---------------------------------------
@x [19] m.279 l.5995 geq_word_define - e-TeX tracing
begin eqtb[p].int:=w; xeq_level[p]:=level_one;
@y
begin assign_trace(p,"globally changing")@;@/
begin eqtb[p].int:=w; xeq_level[p]:=level_one;
end;
assign_trace(p,"into")@;@/
@z
%---------------------------------------
@x [19] m.281 l.6012 - e-TeX tracing
@p@t\4@>@<Declare the procedure called |restore_trace|@>@;@/
@y
@p
@z
%---------------------------------------
@x [19] m.281 l.6019 unsave - e-TeX optimized \aftergroup
begin if cur_level>level_one then
@y
@!a:boolean; {have we already processed an \.{\\aftergroup} ?}
begin a:=false;
if cur_level>level_one then
@z
%---------------------------------------
@x [19] m.282 l.6033 - e-TeX sparse arrays
  else  begin if save_type(save_ptr)=restore_old_value then
@y
  else if save_type(save_ptr)=restore_sa then
    begin sa_restore; sa_chain:=p; sa_level:=save_level(save_ptr);
    end
  else  begin if save_type(save_ptr)=restore_old_value then
@z
%---------------------------------------
@x [19] m.282 l.6041 - e-TeX tracing
done: cur_group:=save_level(save_ptr); cur_boundary:=save_index(save_ptr)
@y
done: @!stat if tracing_groups>0 then group_trace(true);@+tats@;@/
if grp_stack[in_open]=cur_boundary then group_warning;
  {groups possibly not properly nested with files}
cur_group:=save_level(save_ptr); cur_boundary:=save_index(save_ptr);
if eTeX_ex then decr(save_ptr)
@z
%---------------------------------------
@x [19] m.284 l.6067 - e-TeX tracing
@ @<Declare the procedure called |restore_trace|@>=
@y
@ @<Declare \eTeX\ procedures for tr...@>=
@z
%---------------------------------------
@x [20] m.289 l.6155 - e-TeX protected
@d end_match_token=@'7000 {$2^8\cdot|end_match|$}
@y
@d end_match_token=@'7000 {$2^8\cdot|end_match|$}
@d protected_token=@'7001 {$2^8\cdot|end_match|+1$}
@z
%---------------------------------------
@x [20] m.294 l.6280 - e-TeX protected
end_match: print("->");
@y
end_match: if c=0 then print("->");
@z
%---------------------------------------
@x [20] m.296 l.6301 print_meaning - e-TeX marks
else if cur_cmd=top_bot_mark then
@y
else if (cur_cmd=top_bot_mark)and(cur_chr<marks_code) then
@z
%---------------------------------------
@x [21] m.298 l.6375 print_cmd_chr - e-TeX protected
procedure print_cmd_chr(@!cmd:quarterword;@!chr_code:halfword);
@y
procedure print_cmd_chr(@!cmd:quarterword;@!chr_code:halfword);
var n:integer; {temp variable}
@z
%---------------------------------------
@x [21] m.299 l.6394 show_cur_cmd_chr - e-TeX tracing
@p procedure show_cur_cmd_chr;
@y
@p procedure show_cur_cmd_chr;
var n:integer; {level of \.{\\if...\\fi} nesting}
@!l:integer; {line where \.{\\if} started}
@!p:pointer;
@z
%---------------------------------------
@x [21] m.299 l.6399 show_cur_cmd_chr - e-TeX tracing
print_cmd_chr(cur_cmd,cur_chr); print_char("}");
@y
print_cmd_chr(cur_cmd,cur_chr);
if tracing_ifs>0 then
  if cur_cmd>=if_test then if cur_cmd<=fi_or_else then
    begin print(": ");
    if cur_cmd=fi_or_else then
      begin print_cmd_chr(if_test,cur_if); print_char(" ");
      n:=0; l:=if_line;
      end
    else  begin n:=1; l:=line;
      end;
    p:=cond_ptr;
    while p<>null do
      begin incr(n); p:=link(p);
      end;
    print("(level "); print_int(n); print_char(")"); print_if_line(l);
    end;
print_char("}");
@z
%---------------------------------------
@x [22] m.303 l.6475 show_context - e-TeX scan_tokens
the terminal, under control of the procedure |read_toks|.)
@y
the terminal, under control of the procedure |read_toks|.)
Finally |18<=name<=19| indicates that we are reading a pseudo file
created by the \.{\\scantokens} command.
@z
%---------------------------------------
@x [22] m.307 l.6692 - e-TeX basic
@d mark_text=14 {|token_type| code for \.{\\topmark}, etc.}
@d write_text=15 {|token_type| code for \.{\\write}}
@y
@d every_eof_text=14 {|token_type| code for \.{\\everyeof}}
@d mark_text=15 {|token_type| code for \.{\\topmark}, etc.}
@d write_text=16 {|token_type| code for \.{\\write}}
@z
%---------------------------------------
@x [22] m.311 l.6749 show_context - e-TeX scan_tokens
    if (name>17) or (base_ptr=0) then bottom_line:=true;
@y
    if (name>19) or (base_ptr=0) then bottom_line:=true;
@z
%---------------------------------------
@x [22] m.313 l.6794 - e-TeX scan_tokens
else  begin print_nl("l."); print_int(line);
@y
else if index<>in_open then {input from a pseudo file}
  begin print_nl("l."); print_int(line_stack[index+1]);
  end
else  begin print_nl("l."); print_int(line);
@z
%---------------------------------------
@x [22] m.314 l.6814 - e-TeX basic
every_cr_text: print_nl("<everycr> ");
@y
every_cr_text: print_nl("<everycr> ");
every_eof_text: print_nl("<everyeof> ");
@z
%---------------------------------------
@x [23] m.326 l.7009 - e-TeX optimized \aftergroup
begin t:=cur_tok; cur_tok:=p; back_input; cur_tok:=t;
@y
begin t:=cur_tok; cur_tok:=p;
if a then
  begin p:=get_avail; info(p):=cur_tok; link(p):=loc; loc:=p; start:=p;
  if cur_tok<right_brace_limit then
    if cur_tok<left_brace_limit then decr(align_state)
    else incr(align_state);
  end
else  begin back_input; a:=eTeX_ex;
  end;
cur_tok:=t;
@z
%---------------------------------------
@x [23] m.328 l.7037 begin_file_reading - e-TeX every_eof, tracing_nesting
incr(in_open); push_input; index:=in_open;
@y
incr(in_open); push_input; index:=in_open;
eof_seen[index]:=false;
grp_stack[index]:=cur_boundary; if_stack[index]:=cond_ptr;
@z
%---------------------------------------
@x [23] m.329 l.7047 end_file_reading - e-TeX scan_tokens
if name>17 then a_close(cur_file); {forget it}
@y
if (name=18)or(name=19) then pseudo_close else
if name>17 then a_close(cur_file); {forget it}
@z
%---------------------------------------
@x [23] m.331 l.7066 - e-TeX tracing_nesting
in_open:=0; open_parens:=0; max_buf_stack:=0;
@y
in_open:=0; open_parens:=0; max_buf_stack:=0;
grp_stack[0]:=0; if_stack[0]:=null;
@z
%---------------------------------------
@x [24] m.362 l.7538 - e-TeX scan_tokens, every_eof
if not force_eof then
@y
if not force_eof then
  if name<=19 then
    begin if pseudo_input then {not end of file}
      firm_up_the_line {this sets |limit|}
    else if (every_eof<>null)and not eof_seen[index] then
      begin limit:=first-1; eof_seen[index]:=true; {fake one empty line}
      begin_token_list(every_eof,every_eof_text); goto restart;
      end
    else force_eof:=true;
    end
  else
@z
%---------------------------------------
@x [24] m.362 l.7541 - e-TeX every_eof
  else force_eof:=true;
@y
  else if (every_eof<>null)and not eof_seen[index] then
    begin limit:=first-1; eof_seen[index]:=true; {fake one empty line}
    begin_token_list(every_eof,every_eof_text); goto restart;
    end
  else force_eof:=true;
@z
%---------------------------------------
@x [24] m.362 l.7544 - e-TeX scan_tokens
  begin print_char(")"); decr(open_parens);
  update_terminal; {show user that file has been read}
@y
  begin if tracing_nesting>0 then
    if (grp_stack[in_open]<>cur_boundary)or@|
        (if_stack[in_open]<>cond_ptr) then file_warning;
    {give warning for some unfinished groups and/or conditionals}
  if name>=19 then
  begin print_char(")"); decr(open_parens);
  update_terminal; {show user that file has been read}
  end;
@z
%---------------------------------------
@x [25] m.366 l.7630 - e-TeX basic
@t\4@>@<Declare the procedure called |insert_relax|@>@;@/
@y
@t\4@>@<Declare the procedure called |insert_relax|@>@;@/
@t\4@>@<Declare \eTeX\ procedures for expanding@>@;@/
@z
%---------------------------------------
@x [25] m.366 l.7637 expand - e-TeX cond
procedure expand;
@y
procedure expand;
label reswitch;
@z
%---------------------------------------
@x [25] m.366 l.7648 expand - e-TeX cond
if cur_cmd<call then @<Expand a nonmacro@>
@y
reswitch:
if cur_cmd<call then @<Expand a nonmacro@>
@z
%---------------------------------------
@x [25] m.367 l.7659 - e-TeX cond
expand_after:@<Expand the token after the next token@>;
@y
expand_after:if cur_chr=0 then @<Expand the token after the next token@>
  else @<Negate a boolean conditional and |goto reswitch|@>;
@z
%---------------------------------------
@x [25] m.377 l.7779 - e-TeX scan_tokens
input: if chr_code=0 then print_esc("input")@+else print_esc("endinput");
@y
input: if chr_code=0 then print_esc("input")
  @/@<Cases of |input| for |print_cmd_chr|@>@/
  else print_esc("endinput");
@z
%---------------------------------------
@x [25] m.378 l.7782 - e-TeX scan_tokens
if cur_chr>0 then force_eof:=true
@y
if cur_chr=1 then force_eof:=true
@/@<Cases for |input|@>@/
@z
%---------------------------------------
@x [25] m.382 l.7838 - e-TeX marks
@d top_mark_code=0 {the mark in effect at the previous page break}
@y
@d marks_code==5 {add this for \.{\\topmarks} etc.}
@#
@d top_mark_code=0 {the mark in effect at the previous page break}
@z
%---------------------------------------
@x [25] m.385 l.7870 - e-TeX marks
top_bot_mark: case chr_code of
@y
top_bot_mark: begin case (chr_code mod marks_code) of
@z
%---------------------------------------
@x [25] m.385 l.7876 - e-TeX marks
  endcases;
@y
  endcases;
  if chr_code>=marks_code then print_char("s");
  end;
@z
%---------------------------------------
@x [25] m.386 l.7882 - e-TeX marks
begin if cur_mark[cur_chr]<>null then
  begin_token_list(cur_mark[cur_chr],mark_text);
@y
begin t:=cur_chr mod marks_code;
if cur_chr>=marks_code then scan_register_num@+else cur_val:=0;
if cur_val=0 then cur_ptr:=cur_mark[t]
else @<Compute the mark pointer for mark type |t| and class |cur_val|@>;
if cur_ptr<>null then begin_token_list(cur_ptr,mark_text);
@z
%---------------------------------------
@x [25] m.389 l.7945 macro_call - e-TeX protected
if info(r)<>end_match_token then
@y
if info(r)=protected_token then r:=link(r);
if info(r)<>end_match_token then
@z
%---------------------------------------
@x [26] m.409 l.8255 - e-TeX basic
@t\4\4@>@<Declare procedures that scan font-related stuff@>
@y
@t\4\4@>@<Declare \eTeX\ procedures for scanning@>@;
@t\4\4@>@<Declare procedures that scan font-related stuff@>
@z
%---------------------------------------
@x [26] m.411 l.8299 - e-TeX sparse arrays
|glue_val|, or |mu_val|.
@y
|glue_val|, or |mu_val| more than |mem_bot| (dynamic variable-size nodes
cannot have these values)
@z
%---------------------------------------
@x [26] m.411 l.8302 - e-TeX sparse arrays
primitive("count",register,int_val);
@!@:count_}{\.{\\count} primitive@>
primitive("dimen",register,dimen_val);
@!@:dimen_}{\.{\\dimen} primitive@>
primitive("skip",register,glue_val);
@!@:skip_}{\.{\\skip} primitive@>
primitive("muskip",register,mu_val);
@y
primitive("count",register,mem_bot+int_val);
@!@:count_}{\.{\\count} primitive@>
primitive("dimen",register,mem_bot+dimen_val);
@!@:dimen_}{\.{\\dimen} primitive@>
primitive("skip",register,mem_bot+glue_val);
@!@:skip_}{\.{\\skip} primitive@>
primitive("muskip",register,mem_bot+mu_val);
@z
%---------------------------------------
@x [26] m.412 l.8312 - e-TeX sparse arrays
register: if chr_code=int_val then print_esc("count")
  else if chr_code=dimen_val then print_esc("dimen")
  else if chr_code=glue_val then print_esc("skip")
  else print_esc("muskip");
@y
register: @<Cases of |register| for |print_cmd_chr|@>;
@z
%---------------------------------------
@x [26] m.413 l.8328 scan_something_internal - e-TeX basic
var m:halfword; {|chr_code| part of the operand token}
@y
label exit;
var m:halfword; {|chr_code| part of the operand token}
@!q:halfword; {general purpose index}
@!i:four_quarters; {character info}
@z
%---------------------------------------
@x [26] m.413 l.8354 scan_something_internal - e-TeX basic
end;
@y
exit:end;
@z
%---------------------------------------
@x [26] m.415 l.8375 - e-TeX sparse arrays
    begin scan_eight_bit_int; m:=toks_base+cur_val;
    end;
  scanned_result(equiv(m))(tok_val);
@y
    if m=mem_bot then
      begin scan_register_num;
      if cur_val<256 then cur_val:=equiv(toks_base+cur_val)
      else  begin find_sa_element(tok_val,cur_val,false);
        if cur_ptr=null then cur_val:=null
        else cur_val:=sa_ptr(cur_ptr);
        end;
      end
    else cur_val:=sa_ptr(m)
  else cur_val:=equiv(m);
  cur_val_level:=tok_val;
@z
%---------------------------------------
@x [26] m.416 l.8390 - e-TeX basic
|glue_val|, |input_line_no_code|, or |badness_code|.

@d input_line_no_code=glue_val+1 {code for \.{\\inputlineno}}
@d badness_code=glue_val+2 {code for \.{\\badness}}
@y
|glue_val|, |last_node_type_code|, |input_line_no_code|, |badness_code|,
|eTeX_version_code|, or one of the other codes for \eTeX\ extensions.

@d last_node_type_code=glue_val+1 {code for \.{\\lastnodetype}}
@d input_line_no_code=glue_val+2 {code for \.{\\inputlineno}}
@d badness_code=glue_val+3 {code for \.{\\badness}}
@d eTeX_int=glue_val+4 {first of \eTeX\ codes for integers}
@d eTeX_dim=eTeX_int+8 {first of \eTeX\ codes for dimensions}
@d eTeX_glue=eTeX_dim+9 {first of \eTeX\ codes for glue}
@d eTeX_mu=eTeX_glue+1 {first of \eTeX\ codes for muglue}
@d eTeX_expr=eTeX_mu+1 {first of \eTeX\ codes for expressions}
@z
%---------------------------------------
@x [26] m.417 l.8425 - e-TeX interaction_mode
@+else print_esc("insertpenalties");
@y
@/@<Cases of |set_page_int| for |print_cmd_chr|@>@/
@+else print_esc("insertpenalties");
@z
%---------------------------------------
@x [26] m.417 l.8434 - e-TeX basic
  othercases print_esc("badness")
@y
  @/@<Cases of |last_item| for |print_cmd_chr|@>@/
  othercases print_esc("badness")
@z
%---------------------------------------
@x [26] m.419 l.8457 - e-TeX interaction_mode
begin if m=0 then cur_val:=dead_cycles@+else cur_val:=insert_penalties;
@y
begin if m=0 then cur_val:=dead_cycles
@/@<Cases for `Fetch the |dead_cycles| or the |insert_penalties|'@>@/
else cur_val:=insert_penalties;
@z
%---------------------------------------
@x [26] m.420 l.8462 - e-TeX sparse arrays
begin scan_eight_bit_int;
if box(cur_val)=null then cur_val:=0 @+else cur_val:=mem[box(cur_val)+m].sc;
@y
begin scan_register_num; fetch_box(q);
if q=null then cur_val:=0 @+else cur_val:=mem[q+m].sc;
@z
%---------------------------------------
@x [26] m.423 l.8487 - e-TeX penalties
begin if par_shape_ptr=null then cur_val:=0
@y
begin if m>par_shape_loc then @<Fetch a penalties array element@>
else if par_shape_ptr=null then cur_val:=0
@z
%---------------------------------------
@x [26] m.424 l.8493 - e-TeX TeXXeT
implemented. The reference count for \.{\\lastskip} will be updated later.
@y
implemented. The reference count for \.{\\lastskip} will be updated later.
A final \.{\\endM} node is temporarily removed.
@z
%---------------------------------------
@x [26] m.424 l.8499 - e-TeX basic
if cur_chr>glue_val then
  begin if cur_chr=input_line_no_code then cur_val:=line
  else cur_val:=last_badness; {|cur_chr=badness_code|}
@y
if m>last_node_type_code then
 if m>=eTeX_glue then @<Process an expression and |return|@>@;
 else if m>=eTeX_dim then
  begin case m of
  @/@<Cases for fetching a dimension value@>@/
  end; {there are no other cases}
  cur_val_level:=dimen_val;
  end
 else begin case m of
  input_line_no_code: cur_val:=line;
  badness_code: cur_val:=last_badness;
  @/@<Cases for fetching an integer value@>@/
  end; {there are no other cases}
@z
%---------------------------------------
@x [26] m.424 l.8505 - e-TeX last_node_type
  cur_val_level:=cur_chr;
@y
  if cur_chr=last_node_type_code then
    begin cur_val:=int_val;
    if (tail=head)or(mode=0) then cur_val:=-1;
    end
  else cur_val_level:=cur_chr;
@z
%---------------------------------------
@x [26] m.424 l.8507 - e-TeX TeXXeT
    case cur_chr of
@y
    begin if (type(tail)=math_node)and(subtype(tail)=end_M_code) then
      remove_end_M;
    case cur_chr of
@z
%---------------------------------------
@x [26] m.424 l.8513 - e-TeX last_node_type
      end;
@y
      end;
    last_node_type_code:
      if (type(tail)<>math_node)or(subtype(tail)<>end_M_code) then
        if type(tail)<=unset_node then cur_val:=type(tail)+1
        else cur_val:=unset_node+2;
@z
%---------------------------------------
@x [26] m.424 l.8514 - e-TeX TeXXeT
    end {there are no other cases}
@y
    end; {there are no other cases}
    if LR_temp<>null then insert_end_M;
    end
@z
%---------------------------------------
@x [26] m.424 l.8519 - e-TeX last_node_type
    glue_val: if last_glue<>max_halfword then cur_val:=last_glue;
@y
    glue_val: if last_glue<>max_halfword then cur_val:=last_glue;
    last_node_type_code: cur_val:=last_node_type;
@z
%---------------------------------------
@x [26] m.427 l.8535 - e-TeX sparse arrays
begin scan_eight_bit_int;
case m of
@y
begin if (m<mem_bot)or(m>lo_mem_stat_max) then
  begin cur_val_level:=sa_type(m);
  if cur_val_level<glue_val then cur_val:=sa_int(m)
  else cur_val:=sa_ptr(m);
  end
else  begin scan_register_num; cur_val_level:=m-mem_bot;
  if cur_val>255 then
    begin find_sa_element(cur_val_level,cur_val,false);
    if cur_ptr=null then
      if cur_val_level<glue_val then cur_val:=0
      else cur_val:=zero_glue
    else if cur_val_level<glue_val then cur_val:=sa_int(cur_ptr)
    else cur_val:=sa_ptr(cur_ptr);
    end
  else
  case cur_val_level of
@z
%---------------------------------------
@x [26] m.427 l.8542 - e-TeX sparse arrays
cur_val_level:=m;
@y
  end;
@z
%---------------------------------------
@x [26] m.461 l.9070 - e-TeX expr
exit:end;
@y
exit:end;
@#
@<Declare procedures needed for expressions@>@;
@z
%---------------------------------------
@x [27] m.464 l.9129 - e-TeX basic
@p function str_toks(@!b:pool_pointer):pointer;
@y
@p @t\4@>@<Declare \eTeX\ procedures for token lists@>@;@/
function str_toks(@!b:pool_pointer):pointer;
@z
%---------------------------------------
@x [27] m.465 l.9154 the_toks - e-TeX unexpanded
@p function the_toks:pointer;
@y
@p function the_toks:pointer;
label exit;
@z
%---------------------------------------
@x [27] m.465 l.9158 the_toks - e-TeX unexpanded
begin get_x_token; scan_something_internal(tok_val,false);
@y
@!c:small_number; {value of |cur_chr|}
begin @<Handle \.{\\unexpanded} or \.{\\detokenize} and |return|@>;@/
get_x_token; scan_something_internal(tok_val,false);
@z
%---------------------------------------
@x [27] m.465 l.9172 the_toks - e-TeX unexpanded
end;
@y
exit:end;
@z
%---------------------------------------
@x [27] m.469 l.9223 - e-TeX basic
  othercases print_esc("jobname")
@y
  @/@<Cases of |convert| for |print_cmd_chr|@>@/
  othercases print_esc("jobname")
@z
%---------------------------------------
@x [27] m.470 l.9232 conv_toks - e-TeX basic
@!c:number_code..job_name_code; {desired type of conversion}
@y
@!c:small_number; {desired type of conversion}
@z
%---------------------------------------
@x [27] m.471 l.9249 - e-TeX basic
end {there are no other cases}
@y
@/@<Cases of `Scan the argument for command |c|'@>@/
end {there are no other cases}
@z
%---------------------------------------
@x [27] m.472 l.9265 - e-TeX basic
end {there are no other cases}
@y
@/@<Cases of `Print the result of command |c|'@>@/
end {there are no other cases}
@z
%---------------------------------------
@x [27] m.478 l.9374 - e-TeX protected
  if cur_cmd<=max_command then goto done2;
@y
  if cur_cmd>=call then
    if info(link(cur_chr))=protected_token then
      begin cur_cmd:=relax; cur_chr:=no_expand_flag;
      end;
  if cur_cmd<=max_command then goto done2;
@z
%---------------------------------------
@x [27] m.482 l.9422 read_toks - e-TeX read_line
@p procedure read_toks(@!n:integer;@!r:pointer);
@y
@p procedure read_toks(@!n:integer;@!r:pointer;@!j:halfword);
@z
%---------------------------------------
@x [27] m.483 l.9448 - e-TeX read_line
loop@+  begin get_token;
@y
@<Handle \.{\\readline} and |goto done|@>;@/
loop@+  begin get_token;
@z
%---------------------------------------
@x [28] m.487 l.9500 - e-TeX cond
@d if_char_code=0 { `\.{\\if}' }
@y
@d unless_code=32 {amount added for `\.{\\unless}' prefix}
@#
@d if_char_code=0 { `\.{\\if}' }
@z
%---------------------------------------
@x [28] m.488 l.9555 - e-TeX cond
if_test: case chr_code of
@y
if_test: begin if chr_code>=unless_code then print_esc("unless");
case chr_code mod unless_code of
@z
%---------------------------------------
@x [28] m.488 l.9572 - e-TeX cond
  othercases print_esc("if")
  endcases;
@y
  @/@<Cases of |if_test| for |print_cmd_chr|@>@/
  othercases print_esc("if")
  endcases;
end;
@z
%---------------------------------------
@x [28] m.494 l.9646 pass_text - e-TeX tracing
done: scanner_status:=save_scanner_status;
@y
done: scanner_status:=save_scanner_status;
if tracing_ifs>0 then show_cur_cmd_chr;
@z
%---------------------------------------
@x [28] m.496 l.9662 - e-TeX tracing_nesting
begin p:=cond_ptr; if_line:=if_line_field(p);
@y
begin if if_stack[in_open]=cond_ptr then if_warning;
  {conditionals possibly not properly nested with files}
p:=cond_ptr; if_line:=if_line_field(p);
@z
%---------------------------------------
@x [28] m.498 l.9699 conditional - e-TeX cond
begin @<Push the condition stack@>;@+save_cond_ptr:=cond_ptr;this_if:=cur_chr;@/
@<Either process \.{\\ifcase} or set |b| to the value of a boolean condition@>;
@y
@!is_unless:boolean; {was this if preceded by `\.{\\unless}' ?}
begin if tracing_ifs>0 then if tracing_commands<=1 then show_cur_cmd_chr;
@<Push the condition stack@>;@+save_cond_ptr:=cond_ptr;
is_unless:=(cur_chr>=unless_code); this_if:=cur_chr mod unless_code;@/
@<Either process \.{\\ifcase} or set |b| to the value of a boolean condition@>;
if is_unless then b:=not b;
@z
%---------------------------------------
@x [28] m.501 l.9742 - e-TeX cond
if_false_code: b:=false;
@y
if_false_code: b:=false;
@/@<Cases for |conditional|@>@/
@z
%---------------------------------------
@x [28] m.505 l.9781 - e-TeX sparse arrays
begin scan_eight_bit_int; p:=box(cur_val);
@y
begin scan_register_num; fetch_box(p);
@z
%---------------------------------------
@x [28] m.510 l.9871 - e-TeX cond
if cur_chr>if_limit then
@y
begin if tracing_ifs>0 then if tracing_commands<=1 then show_cur_cmd_chr;
if cur_chr>if_limit then
@z
%---------------------------------------
@x [28] m.510 l.9882 - e-TeX cond
  end
@y
  end;
end
@z
%---------------------------------------
@x [29] m.536 l.10324 - e-TeX basic
begin wlog(banner);
@y
begin wlog(eTeX_banner);
@z
%---------------------------------------
@x [29] m.536 l.10331 - e-TeX basic
end
@y
if eTeX_ex then
  begin; wlog_cr; wlog('entering extended mode');
  end;
end
@z
%---------------------------------------
@x [30] m.581 l.11263 char_warning - e-TeX tracing
begin if tracing_lost_chars>0 then
@y
var old_setting: integer; {saved value of |tracing_online|}
begin if tracing_lost_chars>0 then
 begin old_setting:=tracing_online;
 if eTeX_ex and(tracing_lost_chars>1) then tracing_online:=1;
@z
%---------------------------------------
@x [30] m.581 l.11270 char_warning - e-TeX tracing
end;
@y
 tracing_online:=old_setting;
 end;
end;
@z
%---------------------------------------
@x [32] m.616 l.12238 - e-TeX TeXXeT
this is essentially the depth of |push| commands in the \.{DVI} output.
@y
this is essentially the depth of |push| commands in the \.{DVI} output.

For mixed direction text (\TeXXeT) the current text direction is called
|cur_dir|. As the box being shipped out will never be used again and
soon be recycled, we can simply reverse any R-text (i.e., right-to-left)
segments of hlist nodes as well as complete hlist nodes embedded in such
segments. Moreover this can be done iteratively rather than recursively.
There are, however, two complications related to leaders that require
some additional bookkeeping: (1)~One and the same hlist node might be
used more than once (but never inside both L- and R-text); and
(2)~leader boxes inside hlists must be aligned with respect to the left
edge of the original hlist.

A math node is changed into a kern node whenever the text direction
remains the same, it is replaced by an |edge_node| if the text direction
changes; the subtype of an an |hlist_node| inside R-text is changed to
|reversed| once its hlist has been reversed.
@!@^data structure assumptions@>
@z
%---------------------------------------
@x [32] m.616 l.12240 - e-TeX TeXXeT
@d synch_h==if cur_h<>dvi_h then
@y
@d reversed=min_quarterword+1 {subtype for an |hlist_node| whose hlist
  has been reversed}
@d dlist=min_quarterword+2 {subtype for an |hlist_node| from display math mode}
@d left_to_right=0
@d right_to_left=1
@d reflected==1-cur_dir {the opposite of |cur_dir|}
@#
@d synch_h==if cur_h<>dvi_h then
@z
%---------------------------------------
@x [32] m.619 l.12300 hlist_out - e-TeX add_glue
@!g_order: glue_ord; {applicable order of infinity for glue}
@y
@z
%---------------------------------------
@x [32] m.619 l.12308 hlist_out - e-TeX TeXXeT
@!edge:scaled; {left edge of sub-box, or right edge of leader space}
@y
@!edge:scaled; {right edge of sub-box or leader space}
@!prev_p:pointer; {one step behind |p|}
@z
%---------------------------------------
@x [32] m.619 l.12309 hlist_out - e-TeX add_glue
@!glue_temp:real; {glue value before rounding}
begin this_box:=temp_ptr; g_order:=glue_order(this_box);
@y
begin this_box:=temp_ptr;
@z
%---------------------------------------
@x [32] m.619 l.12315 hlist_out - e-TeX TeXXeT
save_loc:=dvi_offset+dvi_ptr; base_line:=cur_v; left_edge:=cur_h;
@y
save_loc:=dvi_offset+dvi_ptr; base_line:=cur_v;
prev_p:=this_box+list_offset;
if eTeX_ex then
  begin @<Initialize the LR stack@>;
  if subtype(this_box)=dlist then
    if cur_dir=right_to_left then
      begin cur_dir:=left_to_right; cur_h:=cur_h-width(this_box);
      end
    else subtype(this_box):=min_quarterword;
  if (cur_dir=right_to_left)and(subtype(this_box)<>reversed) then
    @<Reverse the complete hlist and set the subtype to |reversed|@>;
  end;
left_edge:=cur_h;
@z
%---------------------------------------
@x [32] m.619 l.12318 hlist_out - e-TeX TeXXeT
prune_movements(save_loc);
@y
if eTeX_ex then
  begin @<Check for LR anomalies at the end of |hlist_out|@>;
  if subtype(this_box)=dlist then cur_dir:=right_to_left;
  end;
prune_movements(save_loc);
@z
%---------------------------------------
@x [32] m.620 l.12337 - e-TeX TeXXeT
  p:=link(p);
@y
  prev_p:=link(prev_p); {N.B.: not |prev_p:=p|, |p| might be |lig_trick|}
  p:=link(p);
@z
%---------------------------------------
@x [32] m.622 l.12362 - e-TeX TeXXeT
kern_node,math_node:cur_h:=cur_h+width(p);
@y
kern_node:cur_h:=cur_h+width(p);
math_node:begin if eTeX_ex then
    @<Adjust \(t)the LR stack for the |hlist_out| routine; if necessary
      reverse an hlist segment and |goto reswitch|@>;
  cur_h:=cur_h+width(p);
  end;
@z
%---------------------------------------
@x [32] m.622 l.12364 - e-TeX TeXXeT
othercases do_nothing
@y
@/@<Cases of |hlist_out| that arise in mixed direction text only@>@;
othercases do_nothing
@z
%---------------------------------------
@x [32] m.622 l.12369 - e-TeX TeXXeT
next_p:p:=link(p);
@y
next_p:prev_p:=p; p:=link(p);
@z
%---------------------------------------
@x [32] m.623 l.12376 - e-TeX TeXXeT
  temp_ptr:=p; edge:=cur_h;
@y
  temp_ptr:=p; edge:=cur_h+width(p);
  if cur_dir=right_to_left then cur_h:=edge;
@z
%---------------------------------------
@x [32] m.623 l.12379 - e-TeX TeXXeT
  cur_h:=edge+width(p); cur_v:=base_line;
@y
  cur_h:=edge; cur_v:=base_line;
@z
%---------------------------------------
@x [32] m.625 l.12401 - e-TeX add_glue
  begin if g_sign=stretching then
    begin if stretch_order(g)=g_order then
      begin vet_glue(float(glue_set(this_box))*stretch(g));
@^real multiplication@>
      rule_wd:=rule_wd+round(glue_temp);
      end;
    end
  else if shrink_order(g)=g_order then
    begin vet_glue(float(glue_set(this_box))*shrink(g));
      rule_wd:=rule_wd-round(glue_temp);
    end;
  end;
@y
  add_glue(rule_wd);
@z
%---------------------------------------
@x [32] m.626 l.12428 - e-TeX TeXXeT
  edge:=cur_h+rule_wd; lx:=0;
@y
  if cur_dir=right_to_left then cur_h:=cur_h-10;
  edge:=cur_h+rule_wd; lx:=0;
@z
%---------------------------------------
@x [32] m.626 l.12434 - e-TeX TeXXeT
  cur_h:=edge-10; goto next_p;
@y
  if cur_dir=right_to_left then cur_h:=edge
  else cur_h:=edge-10;
  goto next_p;
@z
%---------------------------------------
@x [32] m.628 l.12473 - e-TeX TeXXeT
synch_h; save_h:=dvi_h; temp_ptr:=leader_box;
@y
synch_h; save_h:=dvi_h; temp_ptr:=leader_box;
if cur_dir=right_to_left then cur_h:=cur_h+leader_wd;
@z
%---------------------------------------
@x [32] m.629 l.12489 vlist_out - e-TeX add_glue
@!g_order: glue_ord; {applicable order of infinity for glue}
@y
@z
%---------------------------------------
@x [32] m.629 l.12498 vlist_out - e-TeX add_glue
@!glue_temp:real; {glue value before rounding}
begin this_box:=temp_ptr; g_order:=glue_order(this_box);
@y
begin this_box:=temp_ptr;
@z
%---------------------------------------
@x [32] m.632 l.12544 - e-TeX TeXXeT
  cur_h:=left_edge+shift_amount(p); {shift the box right}
@y
  if cur_dir=right_to_left then cur_h:=left_edge-shift_amount(p)
  else cur_h:=left_edge+shift_amount(p); {shift the box right}
@z
%---------------------------------------
@x [32] m.633 l.12556 - e-TeX TeXXeT
  begin synch_h; synch_v;
  dvi_out(put_rule); dvi_four(rule_ht); dvi_four(rule_wd);
@y
  begin if cur_dir=right_to_left then cur_h:=cur_h-rule_wd;
  synch_h; synch_v;
  dvi_out(put_rule); dvi_four(rule_ht); dvi_four(rule_wd);
  cur_h:=left_edge;
@z
%---------------------------------------
@x [32] m.634 l.12564 - e-TeX add_glue
  begin if g_sign=stretching then
    begin if stretch_order(g)=g_order then
      begin vet_glue(float(glue_set(this_box))*stretch(g));
@^real multiplication@>
      rule_ht:=rule_ht+round(glue_temp);
      end;
    end
  else if shrink_order(g)=g_order then
    begin vet_glue(float(glue_set(this_box))*shrink(g));
    rule_ht:=rule_ht-round(glue_temp);
    end;
  end;
@y
  add_glue(rule_ht);
@z
%---------------------------------------
@x [32] m.637 l.12619 - e-TeX TeXXeT
begin cur_h:=left_edge+shift_amount(leader_box); synch_h; save_h:=dvi_h;@/
@y
begin if cur_dir=right_to_left then
  cur_h:=left_edge-shift_amount(leader_box)
  else cur_h:=left_edge+shift_amount(leader_box);
synch_h; save_h:=dvi_h;@/
@z
%---------------------------------------
@x [32] m.638 l.12656 ship_out - e-TeX TeXXeT
@<Ship box |p| out@>;
@y
@<Ship box |p| out@>;
if eTeX_ex then @<Check for LR anomalies at the end of |ship_out|@>;
@z
%---------------------------------------
@x [33] m.649 l.12876 hpack - e-TeX TeXXeT
h:=0; @<Clear dimensions to zero@>;
@y
h:=0; @<Clear dimensions to zero@>;
if TeXXeT_en then @<Initialize the LR stack@>;
@z
%---------------------------------------
@x [33] m.649 l.12886 hpack - e-TeX TeXXeT
exit: hpack:=r;
@y
exit: if TeXXeT_en then @<Check for LR anomalies at the end of |hpack|@>;
hpack:=r;
@z
%---------------------------------------
@x [33] m.651 l.12910 - e-TeX TeXXeT
  kern_node,math_node: x:=x+width(p);
@y
  kern_node: x:=x+width(p);
  math_node: begin x:=x+width(p);
    if TeXXeT_en then @<Adjust \(t)the LR stack for the |hpack| routine@>;
    end;
@z
%---------------------------------------
@x [34] m.687 l.13480 - e-TeX middle
\TeX's \.{\\left} and \.{\\right}. The |nucleus| of such noads is
@y
\TeX's \.{\\left} and \.{\\right} as well as \eTeX's \.{\\middle}.
The |nucleus| of such noads is
@z
%---------------------------------------
@x [34] m.687 l.13497 - e-TeX middle
@d delimiter==nucleus {|delimiter| field in left and right noads}
@y
@d delimiter==nucleus {|delimiter| field in left and right noads}
@d middle_noad==1 {|subtype| of right noad representing \.{\\middle}}
@z
%---------------------------------------
@x [34] m.696 l.13670 - e-TeX middle
right_noad: begin print_esc("right"); print_delimiter(nucleus(p));
  end;
end;
if subtype(p)<>normal then
  if subtype(p)=limits then print_esc("limits")
  else print_esc("nolimits");
if type(p)<left_noad then print_subsidiary_data(nucleus(p),".");
@y
right_noad: begin if subtype(p)=normal then print_esc("right")
  else print_esc("middle");
  print_delimiter(nucleus(p));
  end;
end;
if type(p)<left_noad then
  begin if subtype(p)<>normal then
    if subtype(p)=limits then print_esc("limits")
    else print_esc("nolimits");
  print_subsidiary_data(nucleus(p),".");
  end;
@z
%---------------------------------------
@x [36] m.727 l.14268 - e-TeX middle
done_with_noad: r:=q; r_type:=type(r);
@y
done_with_noad: r:=q; r_type:=type(r);
if r_type=right_noad then
  begin r_type:=left_noad; cur_style:=style; @<Set up the values...@>;
  end;
@z
%---------------------------------------
@x [36] m.760 l.14929 - e-TeX middle
  r_type:=t;
@y
  if type(q)=right_noad then t:=open_noad;
  r_type:=t;
@z
%---------------------------------------
@x [36] m.762 l.14970 make_left_right - e-TeX middle
begin if style<script_style then cur_size:=text_size
else cur_size:=16*((style-text_style) div 2);
@y
begin cur_style:=style; @<Set up the values...@>;
@z
%---------------------------------------
@x [37] m.785 l.15461 align_peek - e-TeX protected
begin restart: align_state:=1000000; @<Get the next non-blank non-call token@>;
@y
begin restart: align_state:=1000000;
repeat get_x_or_protected;
until cur_cmd<>spacer;
@z
%---------------------------------------
@x [37] m.791 l.15572 fin_col - e-TeX protected
align_state:=1000000; @<Get the next non-blank non-call token@>;
@y
align_state:=1000000;
repeat get_x_or_protected;
until cur_cmd<>spacer;
@z
%---------------------------------------
@x [37] m.807 l.15834 - e-TeX TeXXeT
  begin type(q):=hlist_node; width(q):=width(p);
@y
  begin type(q):=hlist_node; width(q):=width(p);
  if nest[nest_ptr-1].mode_field=mmode then subtype(q):=dlist; {for |ship_out|}
@z
%---------------------------------------
@x [37] m.808 l.15852 - e-TeX TeXXeT
n:=span_count(r); t:=width(s); w:=t; u:=hold_head;
@y
n:=span_count(r); t:=width(s); w:=t; u:=hold_head;
subtype(r):=min_quarterword; {for |ship_out|}
@z
%---------------------------------------
@x [38] m.814 l.15975 - e-TeX penalties
There is one explicit parameter:  |final_widow_penalty| is the amount of
additional penalty to be inserted before the final line of the paragraph.
@y
There is one explicit parameter:  |d| is true for partial paragraphs
preceding display math mode; in this case the amount of additional
penalty inserted before the final line is |display_widow_penalty|
instead of |widow_penalty|.
@z
%---------------------------------------
@x [38] m.815 l.16002 line_break - e-TeX penalties
procedure line_break(@!final_widow_penalty:integer);
@y
procedure line_break(@!d:boolean);
@z
%---------------------------------------
@x [38] m.815 l.16012 - e-TeX basic
end;
@y
end;
@#
@t\4@>@<Declare \eTeX\ procedures for use by |main_control|@>
@z
%---------------------------------------
@x [38] m.816 l.16032 - e-TeX last_line_fit
link(tail):=new_param_glue(par_fill_skip_code);
@y
link(tail):=new_param_glue(par_fill_skip_code);
last_line_fill:=link(tail);
@z
%---------------------------------------
@x [38] m.819 l.16097 - e-TeX last_line_fit
@d active_node_size=3 {number of words in active nodes}
@y
@d active_node_size_normal=3 {number of words in normal active nodes}
@z
%---------------------------------------
@x [38] m.827 l.16260 - e-TeX last_line_fit
background[6]:=shrink(q)+shrink(r);
@y
background[6]:=shrink(q)+shrink(r);
@<Check for special treatment of last line of paragraph@>;
@z
%---------------------------------------
@x [38] m.829 l.16311 try_break - e-TeX last_line_fit
label exit,done,done1,continue,deactivate;
@y
label exit,done,done1,continue,deactivate,found,not_found;
@z
%---------------------------------------
@x [38] m.845 l.16603 - e-TeX last_line_fit
total_demerits(q):=minimal_demerits[fit_class];
@y
total_demerits(q):=minimal_demerits[fit_class];
if do_last_line_fit then
  @<Store \(a)additional data in the new active node@>;
@z
%---------------------------------------
@x [38] m.846 l.16616 - e-TeX last_line_fit
print(" t="); print_int(total_demerits(q));
@y
print(" t="); print_int(total_demerits(q));
if do_last_line_fit then @<Print additional data in the new active node@>;
@z
%---------------------------------------
@x [38] m.851 l.16715 - e-TeX last_line_fit
if (b>inf_bad)or(pi=eject_penalty) then
@y
if do_last_line_fit then @<Adjust \(t)the additional data for last line@>;
found:
if (b>inf_bad)or(pi=eject_penalty) then
@z
%---------------------------------------
@x [38] m.852 l.16739 - e-TeX last_line_fit
  begin b:=0; fit_class:=decent_fit; {infinite stretch}
@y
  begin if do_last_line_fit then
    begin if cur_p=null then {the last line of a paragraph}
      @<Perform computations for last line and |goto found|@>;
    shortfall:=0;
    end;
  b:=0; fit_class:=decent_fit; {infinite stretch}
@z
%---------------------------------------
@x [38] m.855 l.16796 - e-TeX last_line_fit
  best_place[fit_class]:=break_node(r); best_pl_line[fit_class]:=l;
@y
  best_place[fit_class]:=break_node(r); best_pl_line[fit_class]:=l;
  if do_last_line_fit then
    @<Store \(a)additional data for this feasible break@>;
@z
%---------------------------------------
@x [39] m.863 l.16969 - e-TeX last_line_fit
  end;@+tats@/
@y
  end;@+tats@/
if do_last_line_fit then @<Adjust \(t)the final line of the paragraph@>;
@z
%---------------------------------------
@x [39] m.864 l.16980 - e-TeX last_line_fit
line_number(q):=prev_graf+1; total_demerits(q):=0; link(active):=q;
@y
line_number(q):=prev_graf+1; total_demerits(q):=0; link(active):=q;
if do_last_line_fit then
  @<Initialize additional fields of the first active node@>;
@z
%---------------------------------------
@x [39] m.866 l.17030 - e-TeX TeXXeT
math_node: begin auto_breaking:=(subtype(cur_p)=after); kern_break;
@y
math_node: begin if subtype(cur_p)<L_code then auto_breaking:=end_LR(cur_p);
  kern_break;
@z
%---------------------------------------
@x [39] m.876 l.17192 - e-TeX penalties
post_line_break(final_widow_penalty)
@y
post_line_break(d)
@z
%---------------------------------------
@x [39] m.877 l.17206 post_line_break - e-TeX penalties
procedure post_line_break(@!final_widow_penalty:integer);
@y
procedure post_line_break(@!d:boolean);
@z
%---------------------------------------
@x [39] m.877 l.17216 post_line_break - e-TeX TeXXeT
begin @<Reverse the links of the relevant passive nodes, setting |cur_p| to the
@y
@!LR_ptr:pointer; {stack of LR codes}
begin LR_ptr:=LR_save;
@<Reverse the links of the relevant passive nodes, setting |cur_p| to the
@z
%---------------------------------------
@x [39] m.877 l.17229 post_line_break - e-TeX TeXXeT
prev_graf:=best_line-1;
@y
prev_graf:=best_line-1;
LR_save:=LR_ptr;
@z
%---------------------------------------
@x [39] m.879 l.17259 - e-TeX TeXXeT
  r:=q; {now |type(q)=glue_node|, |kern_node|, |math_node| or |penalty_node|}
@y
  r:=q; {now |type(q)=glue_node|, |kern_node|, |math_node| or |penalty_node|}
  if type(q)=math_node then if TeXXeT_en then
    @<Adjust \(t)the LR stack for the |post_line_break| routine@>;
@z
%---------------------------------------
@x [39] m.880 l.17276 - e-TeX TeXXeT
@<Modify the end of the line to reflect the nature of the break and to include
  \.{\\rightskip}; also set the proper value of |disc_break|@>;
@y
if TeXXeT_en then
  @<Insert LR nodes at the beginning of the current line and adjust
    the LR stack based on LR nodes in this line@>;
@<Modify the end of the line to reflect the nature of the break and to include
  \.{\\rightskip}; also set the proper value of |disc_break|@>;
if TeXXeT_en then @<Insert LR nodes at the end of the current line@>;
@z
%---------------------------------------
@x [39] m.881 l.17299 - e-TeX TeXXeT
    else if (type(q)=math_node)or(type(q)=kern_node) then width(q):=0;
@y
    else if type(q)=kern_node then width(q):=0
    else if type(q)=math_node then
      begin width(q):=0;
      if TeXXeT_en then @<Adjust \(t)the LR stack for the |p...@>;
      end;
@z
%---------------------------------------
@x [39] m.890 l.17395 - e-TeX penalties
  begin pen:=inter_line_penalty;
  if cur_line=prev_graf+1 then pen:=pen+club_penalty;
  if cur_line+2=best_line then pen:=pen+final_widow_penalty;
@y
  begin q:=inter_line_penalties_ptr;
  if q<>null then
    begin r:=cur_line;
    if r>penalty(q) then r:=penalty(q);
    pen:=penalty(q+r);
    end
  else pen:=inter_line_penalty;
  q:=club_penalties_ptr;
  if q<>null then
    begin r:=cur_line-prev_graf;
    if r>penalty(q) then r:=penalty(q);
    pen:=pen+penalty(q+r);
    end
  else if cur_line=prev_graf+1 then pen:=pen+club_penalty;
  if d then q:=display_widow_penalties_ptr
  else q:=widow_penalties_ptr;
  if q<>null then
    begin r:=best_line-cur_line-1;
    if r>penalty(q) then r:=penalty(q);
    pen:=pen+penalty(q+r);
    end
  else if cur_line+2=best_line then
    if d then pen:=pen+display_widow_penalty
    else pen:=pen+widow_penalty;
@z
%---------------------------------------
@x [40] m.891 l.17460 - e-TeX hyph_codes
cur_lang:=init_cur_lang; l_hyf:=init_l_hyf; r_hyf:=init_r_hyf;
@y
cur_lang:=init_cur_lang; l_hyf:=init_l_hyf; r_hyf:=init_r_hyf;
set_hyph_index;
@z
%---------------------------------------
@x [40] m.896 l.17529 - e-TeX hyph_codes
  if lc_code(c)<>0 then
    if (lc_code(c)=c)or(uc_hyph>0) then goto done2
@y
  set_lc_code(c);
  if hc[0]<>0 then
    if (hc[0]=c)or(uc_hyph>0) then goto done2
@z
%---------------------------------------
@x [40] m.897 l.17546 - e-TeX hyph_codes
    if lc_code(c)=0 then goto done3;
    if hn=63 then goto done3;
    hb:=s; incr(hn); hu[hn]:=c; hc[hn]:=lc_code(c); hyf_bchar:=non_char;
@y
    set_lc_code(c);
    if hc[0]=0 then goto done3;
    if hn=63 then goto done3;
    hb:=s; incr(hn); hu[hn]:=c; hc[hn]:=hc[0]; hyf_bchar:=non_char;
@z
%---------------------------------------
@x [40] m.898 l.17572 - e-TeX hyph_codes
  if lc_code(c)=0 then goto done3;
  if j=63 then goto done3;
  incr(j); hu[j]:=c; hc[j]:=lc_code(c);@/
@y
  set_lc_code(c);
  if hc[0]=0 then goto done3;
  if j=63 then goto done3;
  incr(j); hu[j]:=c; hc[j]:=hc[0];@/
@z
%---------------------------------------
@x [42] m.934 l.18211 new_hyph_exceptions - e-TeX hyph_codes
label reswitch, exit, found, not_found;
@y
label reswitch, exit, found, not_found, not_found1;
@z
%---------------------------------------
@x [42] m.934 l.18221 new_hyph_exceptions - e-TeX hyph_codes
set_cur_lang;
@y
set_cur_lang;
@!init if trie_not_ready then
  begin hyph_index:=0; goto not_found1;
  end;
tini@/
set_hyph_index;
not_found1:
@z
%---------------------------------------
@x [42] m.937 l.18253 - e-TeX hyph_codes
else  begin if lc_code(cur_chr)=0 then
@y
else  begin set_lc_code(cur_chr);
  if hc[0]=0 then
@z
%---------------------------------------
@x [42] m.937 l.18261 - e-TeX hyph_codes
    begin incr(n); hc[n]:=lc_code(cur_chr);
@y
    begin incr(n); hc[n]:=hc[0];
@z
%---------------------------------------
@x [43] m.952 l.18549 - e-TeX hyph_codes
trie_root:=compress_trie(trie_root); {identify equivalent subtries}
@y
hyph_root:=compress_trie(hyph_root);
trie_root:=compress_trie(trie_root); {identify equivalent subtries}
@z
%---------------------------------------
@x [43] m.958 l.18637 - e-TeX hyph_codes
if trie_root=0 then {no patterns were given}
@y
if trie_max=0 then {no patterns were given}
@z
%---------------------------------------
@x [43] m.958 l.18641 - e-TeX hyph_codes
else begin trie_fix(trie_root); {this fixes the non-holes in |trie|}
@y
else begin if hyph_root>0 then trie_fix(hyph_root);
  if trie_root>0 then trie_fix(trie_root); {this fixes the non-holes in |trie|}
@z
%---------------------------------------
@x [43] m.960 l.18684 new_patterns - e-TeX hyph_codes
  brace@>;
@y
  brace@>;
  if saving_hyph_codes>0 then
    @<Store hyphenation codes for current language@>;
@z
%---------------------------------------
@x [43] m.966 l.18791 init_trie - e-TeX hyph_codes
@<Move the data into |trie|@>;
@y
if hyph_root<>0 then @<Pack all stored |hyph_codes|@>;
@<Move the data into |trie|@>;
@z
%---------------------------------------
@x [44] m.968 l.18807 - e-TeX saved_items
whenever this is possible without backspacing.
@y
whenever this is possible without backspacing.

When the second argument |s| is |false| the deleted nodes are destroyed,
otherwise they are collected in a list starting at |split_disc|.
@z
%---------------------------------------
@x [44] m.968 l.18814 prune_page_top - e-TeX saved_items
@p function prune_page_top(@!p:pointer):pointer; {adjust top after page break}
var prev_p:pointer; {lags one step behind |p|}
@!q:pointer; {temporary variable for list manipulation}
@y
@p function prune_page_top(@!p:pointer;@!s:boolean):pointer;
  {adjust top after page break}
var prev_p:pointer; {lags one step behind |p|}
@!q,@!r:pointer; {temporary variables for list manipulation}
@z
%---------------------------------------
@x [44] m.968 l.18825 prune_page_top - e-TeX saved_items
    link(prev_p):=p; flush_node_list(q);
@y
    link(prev_p):=p;
    if s then
      begin if split_disc=null then split_disc:=q@+else link(r):=q;
      r:=q;
      end
    else flush_node_list(q);
@z
%---------------------------------------
@x [44] m.977 l.18992 vsplit - e-TeX marks, sparse arrays
@p function vsplit(@!n:eight_bits; @!h:scaled):pointer;
@y
@p @t\4@>@<Declare the function called |do_marks|@>@;
function vsplit(@!n:halfword; @!h:scaled):pointer;
@z
%---------------------------------------
@x [44] m.977 l.18998 vsplit - e-TeX sparse arrays
begin v:=box(n);
@y
begin cur_val:=n; fetch_box(v);
@z
%---------------------------------------
@x [44] m.977 l.18999 vsplit - e-TeX marks, saved_items
if split_first_mark<>null then
@y
flush_node_list(split_disc); split_disc:=null;
if sa_mark<>null then
  if do_marks(vsplit_init,0,sa_mark) then sa_mark:=null;
if split_first_mark<>null then
@z
%---------------------------------------
@x [44] m.977 l.19007 vsplit - e-TeX saved_items
q:=prune_page_top(q); p:=list_ptr(v); free_node(v,box_node_size);
@y
q:=prune_page_top(q,saving_vdiscards>0);
p:=list_ptr(v); free_node(v,box_node_size);
@z
%---------------------------------------
@x [44] m.977 l.19008 vsplit - e-TeX sparse arrays
if q=null then box(n):=null {the |eq_level| of the box stays the same}
else box(n):=vpack(q,natural);
@y
if q<>null then q:=vpack(q,natural);
change_box(q); {the |eq_level| of the box stays the same}
@z
%---------------------------------------
@x [44] m.979 l.19033 - e-TeX marks
    if split_first_mark=null then
@y
    if mark_class(p)<>0 then @<Update the current marks for |vsplit|@>
    else if split_first_mark=null then
@z
%---------------------------------------
@x [45] m.982 l.19167 - e-TeX last_node_type
The variables |last_penalty| and |last_kern| are similar.  And
@y
The variables |last_penalty|, |last_kern|, and |last_node_type|
are similar.  And
@z
%---------------------------------------
@x [45] m.982 l.19180 - e-TeX last_node_type
@!last_kern:scaled; {used to implement \.{\\lastkern}}
@y
@!last_kern:scaled; {used to implement \.{\\lastkern}}
@!last_node_type:integer; {used to implement \.{\\lastnodetype}}
@z
%---------------------------------------
@x [45] m.991 l.19317 - e-TeX last_node_type
last_glue:=max_halfword; last_penalty:=0; last_kern:=0;
@y
last_glue:=max_halfword; last_penalty:=0; last_kern:=0;
last_node_type:=-1;
@z
%---------------------------------------
@x [45] m.996 l.19384 - e-TeX last_node_type
last_penalty:=0; last_kern:=0;
@y
last_penalty:=0; last_kern:=0;
last_node_type:=type(p)+1;
@z
%---------------------------------------
@x [45] m.999 l.19421 - e-TeX saved_items
link(contrib_head):=link(p); link(p):=null; flush_node_list(p)
@y
link(contrib_head):=link(p); link(p):=null;
if saving_vdiscards>0 then
  begin if page_disc=null then page_disc:=p@+else link(tail_page_disc):=p;
  tail_page_disc:=p;
  end
else flush_node_list(p)
@z
%---------------------------------------
@x [45] m.1012 l.19661 fire_up - e-TeX marks
if bot_mark<>null then
@y
if sa_mark<>null then
  if do_marks(fire_up_init,0,sa_mark) then sa_mark:=null;
if bot_mark<>null then
@z
%---------------------------------------
@x [45] m.1012 l.19669 fire_up - e-TeX marks
if (top_mark<>null)and(first_mark=null) then
@y
if sa_mark<>null then
  if do_marks(fire_up_done,0,sa_mark) then sa_mark:=null;
if (top_mark<>null)and(first_mark=null) then
@z
%---------------------------------------
@x [45] m.1014 l.19706 - e-TeX marks
  else if type(p)=mark_node then @<Update the values of
@y
  else if type(p)=mark_node then
    if mark_class(p)<>0 then @<Update the current marks for |fire_up|@>
    else @<Update the values of
@z
%---------------------------------------
@x [45] m.1021 l.19818 - e-TeX saved_items
    ins_ptr(p):=prune_page_top(broken_ptr(r));
@y
    ins_ptr(p):=prune_page_top(broken_ptr(r),false);
@z
%---------------------------------------
@x [45] m.1023 l.19854 - e-TeX saved_items
ship_out(box(255)); box(255):=null;
@y
flush_node_list(page_disc); page_disc:=null;
ship_out(box(255)); box(255):=null;
@z
%---------------------------------------
@x [45] m.1026 l.19896 - e-TeX saved_items
pop_nest; build_page;
@y
flush_node_list(page_disc); page_disc:=null;
pop_nest; build_page;
@z
%---------------------------------------
@x [47] m.1070 l.20697 normal_paragraph - e-TeX penalties
if par_shape_ptr<>null then eq_define(par_shape_loc,shape_ref,null);
@y
if par_shape_ptr<>null then eq_define(par_shape_loc,shape_ref,null);
if inter_line_penalties_ptr<>null then
  eq_define(inter_line_penalties_loc,shape_ref,null);
@z
%---------------------------------------
@x [47] m.1071 l.20718 - e-TeX sparse arrays
|box_flag+255| represent `\.{\\setbox0}' through `\.{\\setbox255}';
codes |box_flag+256| through |box_flag+511| represent `\.{\\global\\setbox0}'
through `\.{\\global\\setbox255}';
code |box_flag+512| represents `\.{\\shipout}'; and codes |box_flag+513|
through |box_flag+515| represent `\.{\\leaders}', `\.{\\cleaders}',
@y
|global_box_flag-1| represent `\.{\\setbox0}' through `\.{\\setbox32767}';
codes |global_box_flag| through |ship_out_flag-1| represent
`\.{\\global\\setbox0}' through `\.{\\global\\setbox32767}';
code |ship_out_flag| represents `\.{\\shipout}'; and codes |leader_flag|
through |leader_flag+2| represent `\.{\\leaders}', `\.{\\cleaders}',
@z
%---------------------------------------
@x [47] m.1071 l.20732 - e-TeX sparse arrays
@d ship_out_flag==box_flag+512 {context code for `\.{\\shipout}'}
@d leader_flag==box_flag+513 {context code for `\.{\\leaders}'}
@y
@d global_box_flag==@'10000100000 {context code for `\.{\\global\\setbox0}'}
@d ship_out_flag==@'10000200000  {context code for `\.{\\shipout}'}
@d leader_flag==@'10000200001  {context code for `\.{\\leaders}'}
@z
%---------------------------------------
@x [47] m.1075 l.20815 box_end - e-TeX sparse arrays
var p:pointer; {|ord_noad| for new box in math mode}
@y
var p:pointer; {|ord_noad| for new box in math mode}
@!a:small_number; {global prefix}
@z
%---------------------------------------
@x [47] m.1077 l.20853 - e-TeX sparse arrays
if box_context<box_flag+256 then
  eq_define(box_base-box_flag+box_context,box_ref,cur_box)
else geq_define(box_base-box_flag-256+box_context,box_ref,cur_box)
@y
begin if box_context<global_box_flag then
  begin cur_val:=box_context-box_flag; a:=0;
  end
else  begin cur_val:=box_context-global_box_flag; a:=4;
  end;
if cur_val<256 then define(box_base+cur_val,box_ref,cur_box)
else sa_def_box;
end
@z
%---------------------------------------
@x [47] m.1079 l.20885 begin_box - e-TeX sparse arrays
@!n:eight_bits; {a box number}
begin case cur_chr of
box_code: begin scan_eight_bit_int; cur_box:=box(cur_val);
  box(cur_val):=null; {the box becomes void, at the same level}
  end;
copy_code: begin scan_eight_bit_int; cur_box:=copy_node_list(box(cur_val));
@y
@!n:halfword; {a box number}
begin case cur_chr of
box_code: begin scan_register_num; fetch_box(cur_box);
  change_box(null); {the box becomes void, at the same level}
  end;
copy_code: begin scan_register_num; fetch_box(q); cur_box:=copy_node_list(q);
@z
%---------------------------------------
@x [47] m.1080 l.20901 - e-TeX TeXXeT
since |head| is a one-word node.
@y
since |head| is a one-word node.
A final \.{\\endM} node is temporarily removed.
@z
%---------------------------------------
@x [47] m.1080 l.20914 - e-TeX TeXXeT
    if (type(tail)=hlist_node)or(type(tail)=vlist_node) then
      @<Remove the last box, unless it's part of a discretionary@>;
@y
    begin if (type(tail)=math_node)and(subtype(tail)=end_M_code) then
      remove_end_M;
    if (type(tail)=hlist_node)or(type(tail)=vlist_node) then
      @<Remove the last box, unless it's part of a discretionary@>;
    if LR_temp<>null then insert_end_M;
    end;
@z
%---------------------------------------
@x [47] m.1082 l.20935 - e-TeX sparse arrays
begin scan_eight_bit_int; n:=cur_val;
@y
begin scan_register_num; n:=cur_val;
@z
%---------------------------------------
@x [47] m.1096 l.21119 - e-TeX penalties, TeXXeT
  else line_break(widow_penalty);
@y
  else line_break(false);
  if LR_save<>null then
    begin flush_list(LR_save); LR_save:=null;
    end;
@z
%---------------------------------------
@x [47] m.1101 l.21175 make_mark - e-TeX marks
begin p:=scan_toks(false,true); p:=get_node(small_node_size);
@y
@!c:halfword; {the mark class}
begin if cur_chr=0 then c:=0
else  begin scan_register_num; c:=cur_val;
  end;
p:=scan_toks(false,true); p:=get_node(small_node_size);
mark_class(p):=c;
@z
%---------------------------------------
@x [47] m.1105 l.21203 - e-TeX TeXXeT
will be deleted, if present.
@y
will be deleted, if present.
A final \.{\\endM} node is temporarily removed.
@z
%---------------------------------------
@x [47] m.1105 l.21213 delete_last - e-TeX TeXXeT
else  begin if not is_char_node(tail) then if type(tail)=cur_chr then
@y
else  begin if not is_char_node(tail) then
  begin if (type(tail)=math_node)and(subtype(tail)=end_M_code) then
    remove_end_M;
  if type(tail)=cur_chr then
@z
%---------------------------------------
@x [47] m.1105 l.21224 delete_last - e-TeX TeXXeT
  end;
@y
  if LR_temp<>null then insert_end_M;
  end;
  end;
@z
%---------------------------------------
@x [47] m.1108 l.21262 - e-TeX saved_items
un_vbox: if chr_code=copy_code then print_esc("unvcopy")
@y
un_vbox: if chr_code=copy_code then print_esc("unvcopy")
  @<Cases of |un_vbox| for |print_cmd_chr|@>@/
@z
%---------------------------------------
@x [47] m.1110 l.21272 unpackage - e-TeX saved_items
label exit;
@y
label done, exit;
@z
%---------------------------------------
@x [47] m.1110 l.21275 unpackage - e-TeX saved_items, sparse arrays
begin c:=cur_chr; scan_eight_bit_int; p:=box(cur_val);
@y
begin if cur_chr>copy_code then @<Handle saved items and |goto done|@>;
c:=cur_chr; scan_register_num; fetch_box(p);
@z
%---------------------------------------
@x [47] m.1110 l.21287 unpackage - e-TeX sparse arrays
else  begin link(tail):=list_ptr(p); box(cur_val):=null;
@y
else  begin link(tail):=list_ptr(p); change_box(null);
@z
%---------------------------------------
@x [47] m.1110 l.21290 unpackage - e-TeX saved_items
while link(tail)<>null do tail:=link(tail);
@y
done:
while link(tail)<>null do tail:=link(tail);
@z
%---------------------------------------
@x [47] m.1130 l.21562 - e-TeX TeXXeT
vmode+halign,hmode+valign:init_align;
@y
vmode+halign:init_align;
hmode+valign:@<Cases of |main_control| for |hmode+valign|@>@; init_align;
@z
%---------------------------------------
@x [48] m.1138 l.21629 init_math - e-TeX TeXXeT
procedure init_math;
label reswitch,found,not_found,done;
var w:scaled; {new or partial |pre_display_size|}
@y
@t\4@>@<Declare subprocedures for |init_math|@>@;
procedure init_math;
label reswitch,found,not_found,done;
var w:scaled; {new or partial |pre_display_size|}
@!j:pointer; {prototype box for display}
@!x:integer; {new |pre_display_direction|}
@z
%---------------------------------------
@x [48] m.1145 l.21687 - e-TeX TeXXeT, penalties
begin if head=tail then {`\.{\\noindent\$\$}' or `\.{\$\${ }\$\$}'}
  begin pop_nest; w:=-max_dimen;
  end
else  begin line_break(display_widow_penalty);@/
@y
begin j:=null; w:=-max_dimen;
if head=tail then {`\.{\\noindent\$\$}' or `\.{\$\${ }\$\$}'}
  @<Prepare for display after an empty paragraph@>
else  begin line_break(true);@/
@z
%---------------------------------------
@x [48] m.1145 l.21700 - e-TeX TeXXeT
eq_word_define(dimen_base+pre_display_size_code,w);
@y
eq_word_define(dimen_base+pre_display_size_code,w);
LR_box:=j;
if eTeX_ex then eq_word_define(int_base+pre_display_direction_code,x);
@z
%---------------------------------------
@x [48] m.1146 l.21708 - e-TeX TeXXeT
v:=shift_amount(just_box)+2*quad(cur_font); w:=-max_dimen;
p:=list_ptr(just_box);
@y
@<Prepare for display after a non-empty paragraph@>;
@z
%---------------------------------------
@x [48] m.1146 l.21723 - e-TeX TeXXeT
done:
@y
done:
@<Finish the natural width computation@>
@z
%---------------------------------------
@x [48] m.1147 l.21734 - e-TeX TeXXeT
kern_node,math_node: d:=width(p);
@y
kern_node: d:=width(p);
@t\4@>@<Cases of `Let |d| be the natural width' that need special treatment@>@;
@z
%---------------------------------------
@x [48] m.1185 l.22243 - e-TeX middle
  if type(q)<>left_noad then confusion("right");
@:this can't happen right}{\quad right@>
  info(numerator(incompleat_noad)):=link(q);
  link(q):=incompleat_noad; link(incompleat_noad):=p;
@y
  if (type(q)<>left_noad)or(delim_ptr=null) then confusion("right");
@:this can't happen right}{\quad right@>
  info(numerator(incompleat_noad)):=link(delim_ptr);
  link(delim_ptr):=incompleat_noad; link(incompleat_noad):=p;
@z
%---------------------------------------
@x [48] m.1189 l.22288 - e-TeX middle
else print_esc("right");
@y
@/@<Cases of |left_right| for |print_cmd_chr|@>@/
else print_esc("right");
@z
%---------------------------------------
@x [48] m.1191 l.22297 math_left_right - e-TeX middle
begin t:=cur_chr;
if (t=right_noad)and(cur_group<>math_left_group) then
@y
@!q:pointer; {resulting mlist}
begin t:=cur_chr;
if (t<>left_noad)and(cur_group<>math_left_group) then
@z
%---------------------------------------
@x [48] m.1191 l.22302 math_left_right - e-TeX middle
  if t=left_noad then
    begin push_math(math_left_group); link(head):=p; tail:=p;
    end
  else  begin p:=fin_mlist(p); unsave; {end of |math_left_group|}
@y
  if t=middle_noad then
    begin type(p):=right_noad; subtype(p):=middle_noad;
    end;
  if t=left_noad then q:=p
  else  begin q:=fin_mlist(p); unsave; {end of |math_left_group|}
    end;
  if t<>right_noad then
    begin push_math(math_left_group); link(head):=q; tail:=p;
    delim_ptr:=p;
    end
  else  begin
@z
%---------------------------------------
@x [48] m.1191 l.22308 math_left_right - e-TeX middle
    info(nucleus(tail)):=p;
@y
    info(nucleus(tail)):=q;
@z
%---------------------------------------
@x [48] m.1192 l.22316 - e-TeX middle
  print_err("Extra "); print_esc("right");
@.Extra \\right.@>
  help1("I'm ignoring a \right that had no matching \left.");
@y
  print_err("Extra ");
  if t=middle_noad then
    begin print_esc("middle");
@.Extra \\middle.@>
    help1("I'm ignoring a \middle that had no matching \left.");
    end
  else  begin print_esc("right");
@.Extra \\right.@>
    help1("I'm ignoring a \right that had no matching \left.");
    end;
@z
%---------------------------------------
@x [48] m.1194 l.22331 after_math - e-TeX TeXXeT
procedure after_math;
@y
@t\4@>@<Declare subprocedures for |after_math|@>@;
procedure after_math;
@z
%---------------------------------------
@x [48] m.1194 l.22338 after_math - e-TeX TeXXeT
begin danger:=false;
@y
begin danger:=false;
@<Retrieve the prototype box@>;
@z
%---------------------------------------
@x [48] m.1194 l.22345 after_math - e-TeX TeXXeT
  mlist_to_hlist; a:=hpack(link(temp_head),natural);
@y
  mlist_to_hlist; a:=hpack(link(temp_head),natural);
  subtype(a):=dlist;
@z
%---------------------------------------
@x [48] m.1194 l.22348 after_math - e-TeX TeXXeT
  danger:=false;
@y
  danger:=false;
  @<Retrieve the prototype box@>;
@z
%---------------------------------------
@x [48] m.1199 l.22435 - e-TeX TeXXeT
w:=width(b); z:=display_width; s:=display_indent;
@y
w:=width(b); z:=display_width; s:=display_indent;
if pre_display_direction<0 then s:=-s-z;
@z
%---------------------------------------
@x [48] m.1199 l.22450 - e-TeX TeXXeT
resume_after_display
@y
@<Flush the prototype box@>;
resume_after_display
@z
%---------------------------------------
@x [48] m.1202 l.22492 - e-TeX TeXXeT
d:=half(z-w);
@y
subtype(b):=dlist;
d:=half(z-w);
@z
%---------------------------------------
@x [48] m.1203 l.22513 - e-TeX TeXXeT
  begin shift_amount(a):=s; append_to_vlist(a);
@y
  begin app_display(j,a,0);
@z
%---------------------------------------
@x [48] m.1204 l.22528 - e-TeX TeXXeT
shift_amount(b):=s+d; append_to_vlist(b)
@y
app_display(j,b,d)
@z
%---------------------------------------
@x [48] m.1205 l.22533 - e-TeX TeXXeT
  shift_amount(a):=s+z-width(a);
  append_to_vlist(a);
@y
  app_display(j,a,z-width(a));
@z
%---------------------------------------
@x [48] m.1206 l.22552 - e-TeX TeXXeT
pop_nest;
@y
flush_node_list(LR_box);
pop_nest;
@z
%---------------------------------------
@x [49] m.1208 l.22577 - e-TeX protected
control sequence can be defined to be `\.{\\long}' or `\.{\\outer}', and
it might or might not be expanded. The prefixes `\.{\\global}', `\.{\\long}',
@y
control sequence can be defined to be `\.{\\long}', `\.{\\protected}',
or `\.{\\outer}', and it might or might not be expanded. The prefixes
`\.{\\global}', `\.{\\long}', `\.{\\protected}',
@z
%---------------------------------------
@x [49] m.1209 l.22603 - e-TeX protected
  else print_esc("global");
@y
  @/@<Cases of |prefix| for |print_cmd_chr|@>@/
  else print_esc("global");
@z
%---------------------------------------
@x [49] m.1211 l.22665 prefixed_command - e-TeX tracing
    @<Discard erroneous prefixes and |return|@>;
@y
    @<Discard erroneous prefixes and |return|@>;
  if tracing_commands>2 then if eTeX_ex then show_cur_cmd_chr;
@z
%---------------------------------------
@x [49] m.1213 l.22686 - e-TeX protected
if (cur_cmd<>def)and(a mod 4<>0) then
@y
if a>=8 then
  begin j:=protected_token; a:=a-8;
  end
else j:=0;
if (cur_cmd<>def)and((a mod 4<>0)or(j<>0)) then
@z
%---------------------------------------
@x [49] m.1218 l.22749 - e-TeX protected
  q:=scan_toks(true,e); define(p,call+(a mod 4),def_ref);
@y
  q:=scan_toks(true,e);
  if j<>0 then
    begin q:=get_avail; info(q):=j; link(q):=link(def_ref);
    link(def_ref):=q;
    end;
  define(p,call+(a mod 4),def_ref);
@z
%---------------------------------------
@x [49] m.1224 l.22840 - e-TeX sparse arrays
  othercases begin scan_eight_bit_int;
@y
  othercases begin scan_register_num;
    if cur_val>255 then
      begin j:=n-count_def_code; {|int_val..box_val|}
      if j>mu_val then j:=tok_val; {|int_val..mu_val| or |tok_val|}
      find_sa_element(j,cur_val,true); add_sa_ref(cur_ptr);
      if j=tok_val then j:=toks_register@+else j:=register;
      define(p,j,cur_ptr);
      end
    else
@z
%---------------------------------------
@x [49] m.1225 l.22853 - e-TeX read_line
read_to_cs: begin scan_int; n:=cur_val;
@y
read_to_cs: begin j:=cur_chr; scan_int; n:=cur_val;
@z
%---------------------------------------
@x [49] m.1225 l.22861 - e-TeX read_line
  p:=cur_cs; read_toks(n,p); define(p,call,cur_val);
@y
  p:=cur_cs; read_toks(n,p,j); define(p,call,cur_val);
@z
%---------------------------------------
@x [49] m.1226 l.22870 - e-TeX sparse arrays
  if cur_cmd=toks_register then
    begin scan_eight_bit_int; p:=toks_base+cur_val;
    end
  else p:=cur_chr; {|p=every_par_loc| or |output_routine_loc| or \dots}
@y
  e:=false; {just in case, will be set |true| for sparse array elements}
  if cur_cmd=toks_register then
    if cur_chr=mem_bot then
      begin scan_register_num;
      if cur_val>255 then
        begin find_sa_element(tok_val,cur_val,true);
        cur_chr:=cur_ptr; e:=true;
        end
      else cur_chr:=toks_base+cur_val;
      end
    else e:=true;
  p:=cur_chr; {|p=every_par_loc| or |output_routine_loc| or \dots}
@z
%---------------------------------------
@x [49] m.1226 l.22880 - e-TeX sparse arrays
    begin define(p,undefined_cs,null); free_avail(def_ref);
    end
  else  begin if p=output_routine_loc then {enclose in curlies}
@y
    begin sa_define(p,null)(p,undefined_cs,null); free_avail(def_ref);
    end
  else  begin if (p=output_routine_loc)and not e then {enclose in curlies}
@z
%---------------------------------------
@x [49] m.1226 l.22888 - e-TeX sparse arrays
    define(p,call,def_ref);
@y
    sa_define(p,def_ref)(p,call,def_ref);
@z
%---------------------------------------
@x [49] m.1227 l.22893 - e-TeX sparse arrays
begin if cur_cmd=toks_register then
  begin scan_eight_bit_int; cur_cmd:=assign_toks; cur_chr:=toks_base+cur_val;
  end;
if cur_cmd=assign_toks then
  begin q:=equiv(cur_chr);
  if q=null then define(p,undefined_cs,null)
  else  begin add_token_ref(q); define(p,call,q);
    end;
  goto done;
  end;
end
@y
if (cur_cmd=toks_register)or(cur_cmd=assign_toks) then
  begin if cur_cmd=toks_register then
    if cur_chr=mem_bot then
      begin scan_register_num;
      if cur_val<256 then q:=equiv(toks_base+cur_val)
      else  begin find_sa_element(tok_val,cur_val,false);
        if cur_ptr=null then q:=null
        else q:=sa_ptr(cur_ptr);
        end;
      end
    else q:=sa_ptr(cur_ptr)
  else q:=equiv(cur_chr);
  if q=null then sa_define(p,null)(p,undefined_cs,null)
  else  begin add_token_ref(q); sa_define(p,q)(p,call,q);
    end;
  goto done;
  end
@z
%---------------------------------------
@x [49] m.1236 l.23009 do_register_command - e-TeX sparse arrays
begin q:=cur_cmd;
@y
@!e:boolean; {does |l| refer to a sparse array element?}
@!w:integer; {integer or dimen value of |l|}
begin q:=cur_cmd;
e:=false; {just in case, will be set |true| for sparse array elements}
@z
%---------------------------------------
@x [49] m.1236 l.23024 do_register_command - e-TeX sparse arrays
if p<glue_val then word_define(l,cur_val)
else  begin trap_zero_glue; define(l,glue_ref,cur_val);
@y
if p<glue_val then sa_word_define(l,cur_val)
else  begin trap_zero_glue; sa_define(l,cur_val)(l,glue_ref,cur_val);
@z
%---------------------------------------
@x [49] m.1237 l.23046 - e-TeX sparse arrays
p:=cur_chr; scan_eight_bit_int;
@y
if (cur_chr<mem_bot)or(cur_chr>lo_mem_stat_max) then
  begin l:=cur_chr; p:=sa_type(l); e:=true;
  end
else  begin p:=cur_chr-mem_bot; scan_register_num;
  if cur_val>255 then
    begin find_sa_element(p,cur_val,true); l:=cur_ptr; e:=true;
    end
  else
@z
%---------------------------------------
@x [49] m.1237 l.23053 - e-TeX sparse arrays
end;
found:
@y
  end;
end;
found: if p<glue_val then@+if e then w:=sa_int(l)@+else w:=eqtb[l].int
else if e then s:=sa_ptr(l)@+else s:=equiv(l)
@z
%---------------------------------------
@x [49] m.1238 l.23059 - e-TeX sparse arrays
  if q=advance then cur_val:=cur_val+eqtb[l].int;
@y
  if q=advance then cur_val:=cur_val+w;
@z
%---------------------------------------
@x [49] m.1239 l.23066 - e-TeX sparse arrays
begin q:=new_spec(cur_val); r:=equiv(l);
@y
begin q:=new_spec(cur_val); r:=s;
@z
%---------------------------------------
@x [49] m.1240 l.23086 - e-TeX sparse arrays
    if p=int_val then cur_val:=mult_integers(eqtb[l].int,cur_val)
    else cur_val:=nx_plus_y(eqtb[l].int,cur_val,0)
  else cur_val:=x_over_n(eqtb[l].int,cur_val)
else  begin s:=equiv(l); r:=new_spec(s);
@y
    if p=int_val then cur_val:=mult_integers(w,cur_val)
    else cur_val:=nx_plus_y(w,cur_val,0)
  else cur_val:=x_over_n(w,cur_val)
else  begin r:=new_spec(s);
@z
%---------------------------------------
@x [49] m.1241 l.23108 - e-TeX sparse arrays
set_box: begin scan_eight_bit_int;
  if global then n:=256+cur_val@+else n:=cur_val;
  scan_optional_equals;
  if set_box_allowed then scan_box(box_flag+n)
@y
set_box: begin scan_register_num;
  if global then n:=global_box_flag+cur_val@+else n:=box_flag+cur_val;
  scan_optional_equals;
  if set_box_allowed then scan_box(n)
@z
%---------------------------------------
@x [49] m.1246 l.23179 alter_integer - e-TeX interaction_mode
var c:0..1; {0 for \.{\\deadcycles}, 1 for \.{\\insertpenalties}}
begin c:=cur_chr; scan_optional_equals; scan_int;
if c=0 then dead_cycles:=cur_val
@y
var c:small_number;
  {0 for \.{\\deadcycles}, 1 for \.{\\insertpenalties}, etc.}
begin c:=cur_chr; scan_optional_equals; scan_int;
if c=0 then dead_cycles:=cur_val
@/@<Cases for |alter_integer|@>@/
@z
%---------------------------------------
@x [49] m.1247 l.23188 alter_box_dimen - e-TeX sparse arrays
@!b:eight_bits; {box number}
begin c:=cur_chr; scan_eight_bit_int; b:=cur_val; scan_optional_equals;
scan_normal_dimen;
if box(b)<>null then mem[box(b)+c].sc:=cur_val;
@y
@!b:pointer; {box register}
begin c:=cur_chr; scan_register_num; fetch_box(b); scan_optional_equals;
scan_normal_dimen;
if b<>null then mem[b+c].sc:=cur_val;
@z
%---------------------------------------
@x [49] m.1248 l.23197 - e-TeX penalties
set_shape: begin scan_optional_equals; scan_int; n:=cur_val;
  if n<=0 then p:=null
@y
set_shape: begin q:=cur_chr; scan_optional_equals; scan_int; n:=cur_val;
  if n<=0 then p:=null
  else if q>par_shape_loc then
    begin n:=(cur_val div 2)+1; p:=get_node(2*n+1); info(p):=n;
    n:=cur_val; mem[p+1].int:=n; {number of penalties}
    for j:=p+2 to p+n+1 do
      begin scan_int; mem[j].int:=cur_val; {penalty values}
      end;
    if not odd(n) then mem[p+n+2].int:=0; {unused}
    end
@z
%---------------------------------------
@x [49] m.1248 l.23207 - e-TeX penalties
  define(par_shape_loc,shape_ref,p);
@y
  define(q,shape_ref,p);
@z
%---------------------------------------
@x [49] m.1292 l.23581 - e-TeX show_groups
  show_lists:print_esc("showlists");
@y
  show_lists:print_esc("showlists");
  @<Cases of |xray| for |print_cmd_chr|@>@;@/
@z
%---------------------------------------
@x [49] m.1293 l.23588 show_whatever - e-TeX show_ifs
var p:pointer; {tail of a token list to show}
@y
var p:pointer; {tail of a token list to show}
@!t:small_number; {type of conditional being shown}
@!m:normal..or_code; {upper bound on |fi_or_else| codes}
@!l:integer; {line where that conditional began}
@!n:integer; {level of \.{\\if...\\fi} nesting}
@z
%---------------------------------------
@x [49] m.1293 l.23594 show_whatever - e-TeX show_groups
othercases @<Show the current value of some parameter or register,
@y
@<Cases for |show_whatever|@>@;@/
othercases @<Show the current value of some parameter or register,
@z
%---------------------------------------
@x [49] m.1295 l.23629 - e-TeX protected
call: print("macro");
long_call: print_esc("long macro");
outer_call: print_esc("outer macro");
long_outer_call: begin print_esc("long"); print_esc("outer macro");
@y
call,long_call,outer_call,long_outer_call: begin n:=cmd-call;
  if info(link(chr_code))=protected_token then n:=n+4;
  if odd(n div 4) then print_esc("protected");
  if odd(n) then print_esc("long");
  if odd(n div 2) then print_esc("outer");
  if n>0 then print_char(" ");
  print("macro");
@z
%---------------------------------------
@x [49] m.1296 l.23637 - e-TeX sparse arrays
begin scan_eight_bit_int; begin_diagnostic;
print_nl("> \box"); print_int(cur_val); print_char("=");
if box(cur_val)=null then print("void")
else show_box(box(cur_val));
@y
begin scan_register_num; fetch_box(p); begin_diagnostic;
print_nl("> \box"); print_int(cur_val); print_char("=");
if p=null then print("void")@+else show_box(p);
@z
%---------------------------------------
@x [50] m.1307 l.23779 - e-TeX basic
dump_int(@$);@/
@y
dump_int(@$);@/
@<Dump the \eTeX\ state@>@/
@z
%---------------------------------------
@x [50] m.1308 l.23794 - e-TeX basic
if x<>@$ then goto bad_fmt; {check that strings are the same}
@y
if x<>@$ then goto bad_fmt; {check that strings are the same}
@/@<Undump the \eTeX\ state@>@/
@z
%---------------------------------------
@x [50] m.1311 l.23848 - e-TeX sparse arrays
dump_int(lo_mem_max); dump_int(rover);
@y
dump_int(lo_mem_max); dump_int(rover);
if eTeX_ex then for k:=int_val to tok_val do dump_int(sa_root[k]);
@z
%---------------------------------------
@x [50] m.1312 l.23871 - e-TeX sparse arrays
undump(lo_mem_stat_max+1)(lo_mem_max)(rover);
@y
undump(lo_mem_stat_max+1)(lo_mem_max)(rover);
if eTeX_ex then for k:=int_val to tok_val do
  undump(null)(lo_mem_max)(sa_root[k]);
@z
%---------------------------------------
@x [50] m.1324 l.24065 - e-TeX hyph_codes
dump_int(trie_max);
@y
dump_int(trie_max);
dump_int(hyph_start);
@z
%---------------------------------------
@x [50] m.1325 l.24093 - e-TeX hyph_codes
undump_size(0)(trie_size)('trie size')(j); @+init trie_max:=j;@+tini
@y
undump_size(0)(trie_size)('trie size')(j); @+init trie_max:=j;@+tini
undump(0)(j)(hyph_start);
@z
%---------------------------------------
@x [51] m.1335 l.24313 final_cleanup - tracing
  print_int(cur_level-level_one); print_char(")");
@y
  print_int(cur_level-level_one); print_char(")");
  if eTeX_ex then show_save_groups;
@z
%---------------------------------------
@x [51] m.1335 l.24336 final_cleanup - e-TeX marks, saved_items
    if cur_mark[c]<>null then delete_token_ref(cur_mark[c]);
@y
    if cur_mark[c]<>null then delete_token_ref(cur_mark[c]);
  if sa_mark<>null then
    if do_marks(destroy_marks,0,sa_mark) then sa_mark:=null;
  for c:=last_box_code to vsplit_code do flush_node_list(disc_ptr[c]);
@z
%---------------------------------------
@x [51] m.1336 l.24345 ] m.1336 l.24340 init_prim - e-TeX basic
begin no_new_control_sequence:=false;
@y
begin no_new_control_sequence:=false;
first:=0;
@z
%---------------------------------------
@x [51] m.1337 l.24360 - e-TeX basic
if (format_ident=0)or(buffer[loc]="&") then
@y
@<Enable \eTeX, if requested@>@;@/
if (format_ident=0)or(buffer[loc]="&") then
@z
%---------------------------------------
@x [51] m.1337 l.24368 - e-TeX basic
  end;
@y
  end;
if eTeX_ex then wterm_ln('entering extended mode');
@z
%---------------------------------------
@x [53] m.1363 l.24715 - e-TeX hyph_codes
adv_past(s)
@y
if subtype(s)=language_node then
  begin cur_lang:=what_lang(s); l_hyf:=what_lhm(s); r_hyf:=what_rhm(s);
  set_hyph_index;
  end
@z
%---------------------------------------
@x [54] m.1379 l.24903 - e-TeX additions
@* \[54] System-dependent changes.
@y
@* \[53a] The extended features of \eTeX.
The program has two modes of operation:  (1)~In \TeX\ compatibility mode
it fully deserves the name \TeX\ and there are neither extended features
nor additional primitive commands.  There are, however, a few
modifications that would be legitimate in any implementation of \TeX\
such as, e.g., preventing inadequate results of the glue to \.{DVI}
unit conversion during |ship_out|.  (2)~In extended mode there are
additional primitive commands and the extended features of \eTeX\ are
available.

The distinction between these two modes of operation initially takes
place when a `virgin' \.{eINITEX} starts without reading a format file.
Later on the values of all \eTeX\ state variables are inherited when
\.{eVIRTEX} (or \.{eINITEX}) reads a format file.

The code below is designed to work for cases where `$|init|\ldots|tini|$'
is a run-time switch.

@<Enable \eTeX, if requested@>=
@!init if (buffer[loc]="*")and(format_ident=" (INITEX)") then
  begin no_new_control_sequence:=false;
  @<Generate all \eTeX\ primitives@>@;
  incr(loc); eTeX_mode:=1; {enter extended mode}
  @<Initialize variables for \eTeX\ extended mode@>@;
  end;
tini@;@/
if not no_new_control_sequence then {just entered extended mode ?}
  no_new_control_sequence:=true@+else

@ The \eTeX\ features available in extended mode are grouped into two
categories:  (1)~Some of them are permanently enabled and have no
semantic effect as long as none of the additional primitives are
executed.  (2)~The remaining \eTeX\ features are optional and can be
individually enabled and disabled.  For each optional feature there is
an \eTeX\ state variable named \.{\\...state}; the feature is enabled,
resp.\ disabled by assigning a positive, resp.\ non-positive value to
that integer.

@d eTeX_state_base=int_base+eTeX_state_code
@d eTeX_state(#)==eqtb[eTeX_state_base+#].int {an \eTeX\ state variable}
@#
@d eTeX_version_code=eTeX_int {code for \.{\\eTeXversion}}
@d eTeX_revision_code=6 {command code for \.{\\eTeXrevision}}

@<Generate all \eTeX...@>=
primitive("lastnodetype",last_item,last_node_type_code);
@!@:last_node_type_}{\.{\\lastnodetype} primitive@>
primitive("eTeXversion",last_item,eTeX_version_code);
@!@:eTeX_version_}{\.{\\eTeXversion} primitive@>
primitive("eTeXrevision",convert,eTeX_revision_code);@/
@!@:eTeX_revision_}{\.{\\eTeXrevision} primitive@>

@ @<Cases of |last_item| for |print_cmd_chr|@>=
last_node_type_code: print_esc("lastnodetype");
eTeX_version_code: print_esc("eTeXversion");

@ @<Cases for fetching an integer value@>=
eTeX_version_code: cur_val:=eTeX_version;

@ @<Cases of |convert| for |print_cmd_chr|@>=
eTeX_revision_code: print_esc("eTeXrevision");

@ @<Cases of `Scan the argument for command |c|'@>=
eTeX_revision_code: do_nothing;

@ @<Cases of `Print the result of command |c|'@>=
eTeX_revision_code: print(eTeX_revision);

@ @d eTeX_ex==(eTeX_mode=1) {is this extended mode?}

@<Glob...@>=
@!eTeX_mode: 0..1; {identifies compatibility and extended mode}

@ @<Initialize table entries...@>=
eTeX_mode:=0; {initially we are in compatibility mode}
@<Initialize variables for \eTeX\ compatibility mode@>@;

@ @<Dump the \eTeX\ state@>=
dump_int(eTeX_mode);
for j:=0 to eTeX_states-1 do eTeX_state(j):=0; {disable all enhancements}

@ @<Undump the \eTeX\ state@>=
undump(0)(1)(eTeX_mode);
if eTeX_ex then
  begin @<Initialize variables for \eTeX\ extended mode@>@;
  end
else  begin @<Initialize variables for \eTeX\ compatibility mode@>@;
  end;

@ The |eTeX_enabled| function simply returns its first argument as
result.  This argument is |true| if an optional \eTeX\ feature is
currently enabled; otherwise, if the argument is |false|, the function
gives an error message.

@<Declare \eTeX\ procedures for use...@>=
function eTeX_enabled(@!b:boolean;@!j:quarterword;@!k:halfword):boolean;
begin if not b then
  begin print_err("Improper "); print_cmd_chr(j,k);
  help1("Sorry, this optional e-TeX feature has been disabled."); error;
  end;
eTeX_enabled:=b;
end;

@ First we implement the additional \eTeX\ parameters in the table of
equivalents.

@<Generate all \eTeX...@>=
primitive("everyeof",assign_toks,every_eof_loc);
@!@:every_eof_}{\.{\\everyeof} primitive@>
primitive("tracingassigns",assign_int,int_base+tracing_assigns_code);@/
@!@:tracing_assigns_}{\.{\\tracingassigns} primitive@>
primitive("tracinggroups",assign_int,int_base+tracing_groups_code);@/
@!@:tracing_groups_}{\.{\\tracinggroups} primitive@>
primitive("tracingifs",assign_int,int_base+tracing_ifs_code);@/
@!@:tracing_ifs_}{\.{\\tracingifs} primitive@>
primitive("tracingscantokens",assign_int,int_base+tracing_scan_tokens_code);@/
@!@:tracing_scan_tokens_}{\.{\\tracingscantokens} primitive@>
primitive("tracingnesting",assign_int,int_base+tracing_nesting_code);@/
@!@:tracing_nesting_}{\.{\\tracingnesting} primitive@>
primitive("predisplaydirection",
  assign_int,int_base+pre_display_direction_code);@/
@!@:pre_display_direction_}{\.{\\predisplaydirection} primitive@>
primitive("lastlinefit",assign_int,int_base+last_line_fit_code);@/
@!@:last_line_fit_}{\.{\\lastlinefit} primitive@>
primitive("savingvdiscards",assign_int,int_base+saving_vdiscards_code);@/
@!@:saving_vdiscards_}{\.{\\savingvdiscards} primitive@>
primitive("savinghyphcodes",assign_int,int_base+saving_hyph_codes_code);@/
@!@:saving_hyph_codes_}{\.{\\savinghyphcodes} primitive@>

@ @d every_eof==equiv(every_eof_loc)

@<Cases of |assign_toks| for |print_cmd_chr|@>=
every_eof_loc: print_esc("everyeof");

@ @<Cases for |print_param|@>=
tracing_assigns_code:print_esc("tracingassigns");
tracing_groups_code:print_esc("tracinggroups");
tracing_ifs_code:print_esc("tracingifs");
tracing_scan_tokens_code:print_esc("tracingscantokens");
tracing_nesting_code:print_esc("tracingnesting");
pre_display_direction_code:print_esc("predisplaydirection");
last_line_fit_code:print_esc("lastlinefit");
saving_vdiscards_code:print_esc("savingvdiscards");
saving_hyph_codes_code:print_esc("savinghyphcodes");

@ In order to handle \.{\\everyeof} we need an array |eof_seen| of
boolean variables.

@<Glob...@>=
@!eof_seen : array[1..max_in_open] of boolean; {has eof been seen?}

@ The |print_group| procedure prints the current level of grouping and
the name corresponding to |cur_group|.

@<Declare \eTeX\ procedures for tr...@>=
procedure print_group(@!e:boolean);
label exit;
begin case cur_group of
  bottom_level: begin print("bottom level"); return;
    end;
  simple_group,semi_simple_group:
    begin if cur_group=semi_simple_group then print("semi ");
    print("simple");
    end;
  hbox_group,adjusted_hbox_group:
    begin if cur_group=adjusted_hbox_group then print("adjusted ");
    print("hbox");
    end;
  vbox_group: print("vbox");
  vtop_group: print("vtop");
  align_group,no_align_group:
    begin if cur_group=no_align_group then print("no ");
    print("align");
    end;
  output_group: print("output");
  disc_group: print("disc");
  insert_group: print("insert");
  vcenter_group: print("vcenter");
  math_group,math_choice_group,math_shift_group,math_left_group:
    begin print("math");
    if cur_group=math_choice_group then print(" choice")
    else if cur_group=math_shift_group then print(" shift")
    else if cur_group=math_left_group then print(" left");
    end;
  end; {there are no other cases}
print(" group (level "); print_int(qo(cur_level)); print_char(")");
if saved(-1)<>0 then
  begin if e then print(" entered at line ") else print(" at line ");
  print_int(saved(-1));
  end;
exit:end;

@ The |group_trace| procedure is called when a new level of grouping
begins (|e=false|) or ends (|e=true|) with |saved(-1)| containing the
line number.

@<Declare \eTeX\ procedures for tr...@>=
@!stat procedure group_trace(@!e:boolean);
begin begin_diagnostic; print_char("{");
if e then print("leaving ") else print("entering ");
print_group(e); print_char("}"); end_diagnostic(false);
end;
tats

@ The \.{\\currentgrouplevel} and \.{\\currentgrouptype} commands return
the current level of grouping and the type of the current group
respectively.

@d current_group_level_code=eTeX_int+1 {code for \.{\\currentgrouplevel}}
@d current_group_type_code=eTeX_int+2 {code for \.{\\currentgrouptype}}

@<Generate all \eTeX...@>=
primitive("currentgrouplevel",last_item,current_group_level_code);
@!@:current_group_level_}{\.{\\currentgrouplevel} primitive@>
primitive("currentgrouptype",last_item,current_group_type_code);
@!@:current_group_type_}{\.{\\currentgrouptype} primitive@>

@ @<Cases of |last_item| for |print_cmd_chr|@>=
current_group_level_code: print_esc("currentgrouplevel");
current_group_type_code: print_esc("currentgrouptype");

@ @<Cases for fetching an integer value@>=
current_group_level_code: cur_val:=cur_level-level_one;
current_group_type_code: cur_val:=cur_group;

@ The \.{\\currentiflevel}, \.{\\currentiftype}, and
\.{\\currentifbranch} commands return the current level of conditionals
and the type and branch of the current conditional.

@d current_if_level_code=eTeX_int+3 {code for \.{\\currentiflevel}}
@d current_if_type_code=eTeX_int+4 {code for \.{\\currentiftype}}
@d current_if_branch_code=eTeX_int+5 {code for \.{\\currentifbranch}}

@<Generate all \eTeX...@>=
primitive("currentiflevel",last_item,current_if_level_code);
@!@:current_if_level_}{\.{\\currentiflevel} primitive@>
primitive("currentiftype",last_item,current_if_type_code);
@!@:current_if_type_}{\.{\\currentiftype} primitive@>
primitive("currentifbranch",last_item,current_if_branch_code);
@!@:current_if_branch_}{\.{\\currentifbranch} primitive@>

@ @<Cases of |last_item| for |print_cmd_chr|@>=
current_if_level_code: print_esc("currentiflevel");
current_if_type_code: print_esc("currentiftype");
current_if_branch_code: print_esc("currentifbranch");

@ @<Cases for fetching an integer value@>=
current_if_level_code: begin q:=cond_ptr; cur_val:=0;
  while q<>null do
    begin incr(cur_val); q:=link(q);
    end;
  end;
current_if_type_code: if cond_ptr=null then cur_val:=0
  else if cur_if<unless_code then cur_val:=cur_if+1
  else cur_val:=-(cur_if-unless_code+1);
current_if_branch_code:
  if (if_limit=or_code)or(if_limit=else_code) then cur_val:=1
  else if if_limit=fi_code then cur_val:=-1
  else cur_val:=0;

@ The \.{\\fontcharwd}, \.{\\fontcharht}, \.{\\fontchardp}, and
\.{\\fontcharic} commands return information about a character in a
font.

@d font_char_wd_code=eTeX_dim {code for \.{\\fontcharwd}}
@d font_char_ht_code=eTeX_dim+1 {code for \.{\\fontcharht}}
@d font_char_dp_code=eTeX_dim+2 {code for \.{\\fontchardp}}
@d font_char_ic_code=eTeX_dim+3 {code for \.{\\fontcharic}}

@<Generate all \eTeX...@>=
primitive("fontcharwd",last_item,font_char_wd_code);
@!@:font_char_wd_}{\.{\\fontcharwd} primitive@>
primitive("fontcharht",last_item,font_char_ht_code);
@!@:font_char_ht_}{\.{\\fontcharht} primitive@>
primitive("fontchardp",last_item,font_char_dp_code);
@!@:font_char_dp_}{\.{\\fontchardp} primitive@>
primitive("fontcharic",last_item,font_char_ic_code);
@!@:font_char_ic_}{\.{\\fontcharic} primitive@>

@ @<Cases of |last_item| for |print_cmd_chr|@>=
font_char_wd_code: print_esc("fontcharwd");
font_char_ht_code: print_esc("fontcharht");
font_char_dp_code: print_esc("fontchardp");
font_char_ic_code: print_esc("fontcharic");

@ @<Cases for fetching a dimension value@>=
font_char_wd_code,
font_char_ht_code,
font_char_dp_code,
font_char_ic_code: begin scan_font_ident; q:=cur_val; scan_char_num;
  if (font_bc[q]<=cur_val)and(font_ec[q]>=cur_val) then
    begin i:=char_info(q)(qi(cur_val));
    case m of
    font_char_wd_code: cur_val:=char_width(q)(i);
    font_char_ht_code: cur_val:=char_height(q)(height_depth(i));
    font_char_dp_code: cur_val:=char_depth(q)(height_depth(i));
    font_char_ic_code: cur_val:=char_italic(q)(i);
    end; {there are no other cases}
    end
  else cur_val:=0;
  end;

@ The \.{\\parshapedimen}, \.{\\parshapeindent}, and \.{\\parshapelength}
commands return the indent and length parameters of the current
\.{\\parshape} specification.

@d par_shape_length_code=eTeX_dim+4 {code for \.{\\parshapelength}}
@d par_shape_indent_code=eTeX_dim+5 {code for \.{\\parshapeindent}}
@d par_shape_dimen_code=eTeX_dim+6 {code for \.{\\parshapedimen}}

@<Generate all \eTeX...@>=
primitive("parshapelength",last_item,par_shape_length_code);
@!@:par_shape_length_}{\.{\\parshapelength} primitive@>
primitive("parshapeindent",last_item,par_shape_indent_code);
@!@:par_shape_indent_}{\.{\\parshapeindent} primitive@>
primitive("parshapedimen",last_item,par_shape_dimen_code);
@!@:par_shape_dimen_}{\.{\\parshapedimen} primitive@>

@ @<Cases of |last_item| for |print_cmd_chr|@>=
par_shape_length_code: print_esc("parshapelength");
par_shape_indent_code: print_esc("parshapeindent");
par_shape_dimen_code: print_esc("parshapedimen");

@ @<Cases for fetching a dimension value@>=
par_shape_length_code,
par_shape_indent_code,
par_shape_dimen_code: begin q:=cur_chr-par_shape_length_code; scan_int;
  if (par_shape_ptr=null)or(cur_val<=0) then cur_val:=0
  else  begin if q=2 then
      begin q:=cur_val mod 2; cur_val:=(cur_val+q)div 2;
      end;
    if cur_val>info(par_shape_ptr) then cur_val:=info(par_shape_ptr);
    cur_val:=mem[par_shape_ptr+2*cur_val-q].sc;
    end;
  cur_val_level:=dimen_val;
  end;

@ The \.{\\showgroups} command displays all currently active grouping
levels.

@d show_groups=4 { \.{\\showgroups} }

@<Generate all \eTeX...@>=
primitive("showgroups",xray,show_groups);
@!@:show_groups_}{\.{\\showgroups} primitive@>

@ @<Cases of |xray| for |print_cmd_chr|@>=
show_groups:print_esc("showgroups");

@ @<Cases for |show_whatever|@>=
show_groups: begin begin_diagnostic; show_save_groups;
  end;

@ @<Types...@>=
@!save_pointer=0..save_size; {index into |save_stack|}

@ The modifications of \TeX\ required for the display produced by the
|show_save_groups| procedure were first discussed by Donald~E. Knuth in
{\sl TUGboat\/} {\bf 11}, 165--170 and 499--511, 1990.
@^Knuth, Donald Ervin@>

In order to understand a group type we also have to know its mode.
Since unrestricted horizontal modes are not associated with grouping,
they are skipped when traversing the semantic nest.

@<Declare \eTeX\ procedures for use...@>=
procedure show_save_groups;
label found1,found2,found,done;
var p:0..nest_size; {index into |nest|}
@!m:-mmode..mmode; {mode}
@!v:save_pointer; {saved value of |save_ptr|}
@!l:quarterword; {saved value of |cur_level|}
@!c:group_code; {saved value of |cur_group|}
@!a:-1..1; {to keep track of alignments}
@!i:integer;
@!j:quarterword;
@!s:str_number;
begin p:=nest_ptr; nest[p]:=cur_list; {put the top level into the array}
v:=save_ptr; l:=cur_level; c:=cur_group;
save_ptr:=cur_boundary; decr(cur_level);@/
a:=1;
print_nl(""); print_ln;
loop@+begin print_nl("### "); print_group(true);
  if cur_group=bottom_level then goto done;
  repeat m:=nest[p].mode_field;
  if p>0 then decr(p) else m:=vmode;
  until m<>hmode;
  print(" (");
  case cur_group of
    simple_group: begin incr(p); goto found2;
      end;
    hbox_group,adjusted_hbox_group: s:="hbox";
    vbox_group: s:="vbox";
    vtop_group: s:="vtop";
    align_group: if a=0 then
        begin if m=-vmode then s:="halign" else s:="valign";
        a:=1; goto found1;
        end
      else  begin if a=1 then print("align entry") else print_esc("cr");
        if p>=a then p:=p-a;
        a:=0; goto found;
        end;
    no_align_group:
      begin incr(p); a:=-1; print_esc("noalign"); goto found2;
      end;
    output_group:
      begin print_esc("output"); goto found;
      end;
    math_group: goto found2;
    disc_group,math_choice_group:
      begin if cur_group=disc_group then print_esc("discretionary")
      else print_esc("mathchoice");
      for i:=1 to 3 do if i<=saved(-2) then print("{}");
      goto found2;
      end;
    insert_group:
      begin if saved(-2)=255 then print_esc("vadjust")
      else  begin print_esc("insert"); print_int(saved(-2));
        end;
      goto found2;
      end;
    vcenter_group: begin s:="vcenter"; goto found1;
      end;
    semi_simple_group: begin incr(p); print_esc("begingroup"); goto found;
      end;
    math_shift_group:
      begin if m=mmode then print_char("$")
      else if nest[p].mode_field=mmode then
        begin print_cmd_chr(eq_no,saved(-2)); goto found;
        end;
      print_char("$"); goto found;
      end;
    math_left_group:
      begin if type(nest[p+1].eTeX_aux_field)=left_noad then print_esc("left")
      else print_esc("middle");
      goto found;
      end;
    end; {there are no other cases}
  @<Show the box context@>;
  found1: print_esc(s); @<Show the box packaging info@>;
  found2: print_char("{");
  found: print_char(")"); decr(cur_level);
  cur_group:=save_level(save_ptr); save_ptr:=save_index(save_ptr)
  end;
done: save_ptr:=v; cur_level:=l; cur_group:=c;
end;

@ @<Show the box packaging info@>=
if saved(-2)<>0 then
  begin print_char(" ");
  if saved(-3)=exactly then print("to") else print("spread");
  print_scaled(saved(-2)); print("pt");
  end

@ @<Show the box context@>=
i:=saved(-4);
if i<>0 then
  if i<box_flag then
    begin if abs(nest[p].mode_field)=vmode then j:=hmove else j:=vmove;
    if i>0 then print_cmd_chr(j,0) else print_cmd_chr(j,1);
    print_scaled(abs(i)); print("pt");
    end
  else if i<ship_out_flag then
    begin if i>=global_box_flag then
      begin print_esc("global"); i:=i-(global_box_flag-box_flag);
      end;
    print_esc("setbox"); print_int(i-box_flag); print_char("=");
    end
  else print_cmd_chr(leader_ship,i-(leader_flag-a_leaders))

@ The |scan_general_text| procedure is much like |scan_toks(false,false)|,
but will be invoked via |expand|, i.e., recursively.
@^recursion@>

@<Declare \eTeX\ procedures for sc...@>=
procedure@?scan_general_text; forward;@t\2@>

@ The token list (balanced text) created by |scan_general_text| begins
at |link(temp_head)| and ends at |cur_val|.  (If |cur_val=temp_head|,
the list is empty.)

@<Declare \eTeX\ procedures for tok...@>=
procedure scan_general_text;
label found;
var s:normal..absorbing; {to save |scanner_status|}
@!w:pointer; {to save |warning_index|}
@!d:pointer; {to save |def_ref|}
@!p:pointer; {tail of the token list being built}
@!q:pointer; {new node being added to the token list via |store_new_token|}
@!unbalance:halfword; {number of unmatched left braces}
begin s:=scanner_status; w:=warning_index; d:=def_ref;
scanner_status:=absorbing; warning_index:=cur_cs;
def_ref:=get_avail; token_ref_count(def_ref):=null; p:=def_ref;
scan_left_brace; {remove the compulsory left brace}
unbalance:=1;
loop@+  begin get_token;
  if cur_tok<right_brace_limit then
    if cur_cmd<right_brace then incr(unbalance)
    else  begin decr(unbalance);
      if unbalance=0 then goto found;
      end;
  store_new_token(cur_tok);
  end;
found: q:=link(def_ref); free_avail(def_ref); {discard reference count}
if q=null then cur_val:=temp_head @+ else cur_val:=p;
link(temp_head):=q;
scanner_status:=s; warning_index:=w; def_ref:=d;
end;

@ The \.{\\showtokens} command displays a token list.

@d show_tokens=5 { \.{\\showtokens} , must be odd! }

@<Generate all \eTeX...@>=
primitive("showtokens",xray,show_tokens);
@!@:show_tokens_}{\.{\\showtokens} primitive@>

@ @<Cases of |xray| for |print_cmd_chr|@>=
show_tokens:print_esc("showtokens");

@ The \.{\\unexpanded} primitive prevents expansion of tokens much as
the result from \.{\\the} applied to a token variable.  The
\.{\\detokenize} primitive converts a token list into a list of
character tokens much as if the token list were written to a file.  We
use the fact that the command modifiers for \.{\\unexpanded} and
\.{\\detokenize} are odd whereas those for \.{\\the} and \.{\\showthe}
are even.

@<Generate all \eTeX...@>=
primitive("unexpanded",the,1);@/
@!@:unexpanded_}{\.{\\unexpanded} primitive@>
primitive("detokenize",the,show_tokens);@/
@!@:detokenize_}{\.{\\detokenize} primitive@>

@ @<Cases of |the| for |print_cmd_chr|@>=
else if chr_code=1 then print_esc("unexpanded")
else print_esc("detokenize")

@ @<Handle \.{\\unexpanded} or \.{\\detokenize} and |return|@>=
if odd(cur_chr) then
  begin c:=cur_chr; scan_general_text;
  if c=1 then the_toks:=cur_val
  else begin old_setting:=selector; selector:=new_string; b:=pool_ptr;
    p:=get_avail; link(p):=link(temp_head);
    token_show(p); flush_list(p);
    selector:=old_setting; the_toks:=str_toks(b);
    end;
  return;
  end

@ The \.{\\showifs} command displays all currently active conditionals.

@d show_ifs=6 { \.{\\showifs} }

@<Generate all \eTeX...@>=
primitive("showifs",xray,show_ifs);
@!@:show_ifs_}{\.{\\showifs} primitive@>

@ @<Cases of |xray| for |print_cmd_chr|@>=
show_ifs:print_esc("showifs");

@
@d print_if_line(#)==if #<>0 then
  begin print(" entered on line "); print_int(#);
  end

@<Cases for |show_whatever|@>=
show_ifs: begin begin_diagnostic; print_nl(""); print_ln;
  if cond_ptr=null then
    begin print_nl("### "); print("no active conditionals");
    end
  else  begin p:=cond_ptr; n:=0;
    repeat incr(n); p:=link(p);@+until p=null;
    p:=cond_ptr; t:=cur_if; l:=if_line; m:=if_limit;
    repeat print_nl("### level "); print_int(n); print(": ");
    print_cmd_chr(if_test,t);
    if m=fi_code then print_esc("else");
    print_if_line(l);
    decr(n); t:=subtype(p); l:=if_line_field(p); m:=type(p); p:=link(p);
    until p=null;
    end;
  end;

@ The \.{\\interactionmode} primitive allows to query and set the
interaction mode.

@<Generate all \eTeX...@>=
primitive("interactionmode",set_page_int,2);
@!@:interaction_mode_}{\.{\\interactionmode} primitive@>

@ @<Cases of |set_page_int| for |print_cmd_chr|@>=
else if chr_code=2 then print_esc("interactionmode")

@ @<Cases for `Fetch the |dead_cycles| or the |insert_penalties|'@>=
else if m=2 then cur_val:=interaction

@ @<Declare \eTeX\ procedures for use...@>=
procedure@?new_interaction; forward;@t\2@>

@ @<Cases for |alter_integer|@>=
else if c=2 then
  begin if (cur_val<batch_mode)or(cur_val>error_stop_mode) then
    begin print_err("Bad interaction mode");
@.Bad interaction mode@>
    help2("Modes are 0=batch, 1=nonstop, 2=scroll, and")@/
    ("3=errorstop. Proceed, and I'll ignore this case.");
    int_error(cur_val);
    end
  else  begin cur_chr:=cur_val; new_interaction;
    end;
  end

@ The |middle| feature of \eTeX\ allows one ore several \.{\\middle}
delimiters to appear between \.{\\left} and \.{\\right}.

@<Generate all \eTeX...@>=
primitive("middle",left_right,middle_noad);
@!@:middle_}{\.{\\middle} primitive@>

@ @<Cases of |left_right| for |print_cmd_chr|@>=
else if chr_code=middle_noad then print_esc("middle")

@ In constructions such as
$$\vbox{\halign{\.{#}\hfil\cr
{}\\vbox to \\vsize\{\cr
\hskip 25pt \\vskip 0pt plus 0.0001fil\cr
\hskip 25pt ...\cr
\hskip 25pt \\vfil\\penalty-200\\vfilneg\cr
\hskip 25pt ...\}\cr}}$$
the stretch components of \.{\\vfil} and \.{\\vfilneg} compensate;
in standard \TeX\ they may get modified in order to prevent arithmetic
overflow during |ship_out| when each of them is multiplied by a large
|glue_set| value.

In \eTeX\ the conversion from stretch or shrink components of glue to
\.{DVI} units is performed by the |do_glue| function defined below.

In extended mode the |do_glue| function adds up the relevant stretch (or
shrink) components of consecutive glue nodes and converts the glue nodes
into equivalent kern nodes; during this process glue specifications may
be recycled.  The accumulated stretch or shrink is then multiplied by
|glue_set(this_box)| and returned as result.  Since one and the same box
may be used several times inside leaders the result is also added to the
width of the first or only kern node; the subtype of the glue node(s)
remains unchanged.  The consecutive glue nodes may be separated by
insert, mark, adjust, kern, and penalty nodes.

@d add_glue(#)==#:=#+do_glue(this_box,p)
@#
@d add_stretch_shrink== {accumulate stretch or shrink amount}
if g_sign=stretching then
  begin if stretch_order(g)=g_order then s:=s+stretch(g);
  end
else  begin if shrink_order(g)=g_order then s:=s-shrink(g);
  end

@<Declare procedures needed in |hlist_out|, |vlist_out|@>=
function do_glue(@!this_box,@!p:pointer):scaled;
label continue, next_p, done;
var q:pointer; {list traverser}
@!g_order: glue_ord; {applicable order of infinity for glue}
@!g_sign: normal..shrinking; {selects type of glue}
@!s:scaled; {accumulated stretch or shrink}
@!glue_temp:real; {glue value before rounding}
begin g_order:=glue_order(this_box); g_sign:=glue_sign(this_box);
s:=0; add_stretch_shrink;
if not eTeX_ex or(subtype(p)>=a_leaders) then goto done;
q:=p;
continue: type(q):=kern_node; width(q):=width(g);
fast_delete_glue_ref(g);
next_p: q:=link(q);
if (q<>null) and not is_char_node(q) then case type(q) of
ins_node,mark_node,adjust_node,kern_node,penalty_node: goto next_p;
glue_node: if subtype(q)<a_leaders then
  begin g:=glue_ptr(q); add_stretch_shrink; goto continue;
  end;
othercases do_nothing
endcases;@/
done: if s<>0 then
  begin vet_glue(float(glue_set(this_box))*s); s:=round(glue_temp);
@^real multiplication@>
  if type(p)=kern_node then width(p):=width(p)+s;
  end;
do_glue:=s;
end;

@ The optional |TeXXeT| feature of \eTeX\ contains the code for mixed
left-to-right and right-to-left typesetting.  This code is inspired by
but different from \TeXeT\ as presented by Donald~E. Knuth and Pierre
MacKay in {\sl TUGboat\/} {\bf 8}, 14--25, 1987.
@^Knuth, Donald Ervin@>
@^MacKay, Pierre@>

In order to avoid confusion with \TeXeT\ the present implementation of
mixed direction typesetting is called \TeXXeT.  It differs from \TeXeT\
in several important aspects:  (1)~Right-to-left text is reversed
explicitely by the |ship_out| routine and is written to a normal \.{DVI}
file without any |begin_reflect| or |end_reflect| commands; (2)~a
|math_node| is (ab)used instead of a |whatsit_node| to record the
\.{\\beginL}, \.{\\endL}, \.{\\beginR}, and \.{\\endR} text direction
primitives in order to keep the influence on the line breaking algorithm
for pure left-to-right text as small as possible; (3)~right-to-left text
interrupted by a displayed equation is automatically resumed after that
equation; and (4)~the |valign| command code with a non-zero command
modifier is (ab)used for the text direction primitives.

Nevertheless there is a subtle difference between \TeX\ and \TeXXeT\
that may influence the line breaking algorithm for pure left-to-right
text.  When a paragraph containing math mode material is broken into
lines \TeX\ may generate lines where math mode material is not enclosed
by properly nested \.{\\mathon} and \.{\\mathoff} nodes.  Unboxing such
lines as part of a new paragraph may have the effect that hyphenation is
attempted for `words' originating from math mode or that hyphenation is
inhibited for words originating from horizontal mode.

In \TeXXeT\ additional \.{\\beginM}, resp.\ \.{\\endM} math nodes are
supplied at the start, resp.\ end of lines such that math mode material
inside a horizontal list always starts with either \.{\\mathon} or
\.{\\beginM} and ends with \.{\\mathoff} or \.{\\endM}.  These
additional nodes are transparent to operations such as \.{\\unskip},
\.{\\lastpenalty}, or \.{\\lastbox} but they do have the effect that
hyphenation is never attempted for `words' originating from math mode
and is never inhibited for words originating from horizontal mode.

@d TeXXeT_state==eTeX_state(TeXXeT_code)
@d TeXXeT_en==(TeXXeT_state>0) {is \TeXXeT\ enabled?}

@<Cases for |print_param|@>=
eTeX_state_code+TeXXeT_code:print_esc("TeXXeTstate");

@ @<Generate all \eTeX...@>=
primitive("TeXXeTstate",assign_int,eTeX_state_base+TeXXeT_code);
@!@:TeXXeT_state_}{\.{\\TeXXeT_state} primitive@>
primitive("beginL",valign,begin_L_code);
@!@:beginL_}{\.{\\beginL} primitive@>
primitive("endL",valign,end_L_code);
@!@:endL_}{\.{\\endL} primitive@>
primitive("beginR",valign,begin_R_code);
@!@:beginR_}{\.{\\beginR} primitive@>
primitive("endR",valign,end_R_code);
@!@:endR_}{\.{\\endR} primitive@>

@ @<Cases of |valign| for |print_cmd_chr|@>=
else case chr_code of
  begin_L_code: print_esc("beginL");
  end_L_code: print_esc("endL");
  begin_R_code: print_esc("beginR");
  othercases print_esc("endR")
  endcases

@ @<Cases of |main_control| for |hmode+valign|@>=
if cur_chr>0 then
  begin if eTeX_enabled(TeXXeT_en,cur_cmd,cur_chr) then
@.Improper \\beginL@>
@.Improper \\endL@>
@.Improper \\beginR@>
@.Improper \\endR@>
    tail_append(new_math(0,cur_chr));
  end
else

@ An hbox with subtype dlist will never be reversed, even when embedded
in right-to-left text.

@<Display if this box is never to be reversed@>=
if (type(p)=hlist_node)and(subtype(p)=dlist) then print(", display")

@ A number of routines are based on a stack of one-word nodes whose
|info| fields contain |end_M_code|, |end_L_code|, or |end_R_code|.  The
top of the stack is pointed to by |LR_ptr|.

When the stack manipulation macros of this section are used below,
variable |LR_ptr| might be the global variable declared here for |hpack|
and |ship_out|, or might be local to |post_line_break|.

@d put_LR(#)==begin temp_ptr:=get_avail; info(temp_ptr):=#;
  link(temp_ptr):=LR_ptr; LR_ptr:=temp_ptr;
  end
@#
@d push_LR(#)==put_LR(end_LR_type(#))
@#
@d pop_LR==begin temp_ptr:=LR_ptr; LR_ptr:=link(temp_ptr);
  free_avail(temp_ptr);
  end

@<Glob...@>=
@!LR_temp:pointer; {holds a temporarily removed \.{\\endM} node}
@!LR_ptr:pointer; {stack of LR codes for |hpack|, |ship_out|, and |init_math|}
@!LR_problems:integer; {counts missing begins and ends}
@!cur_dir:small_number; {current text direction}

@ @<Set init...@>=
LR_temp:=null; LR_ptr:=null; LR_problems:=0; cur_dir:=left_to_right;

@ @<Insert LR nodes at the beg...@>=
begin q:=link(temp_head);
if LR_ptr<>null then
  begin temp_ptr:=LR_ptr; r:=q;
  repeat s:=new_math(0,begin_LR_type(info(temp_ptr))); link(s):=r; r:=s;
  temp_ptr:=link(temp_ptr);