lineno.sty v4.41 2005/11/02 A package to attach line numbers to paragraphs
Stephan I. Böttcher Uwe Lück<EMAIL_ADDRESS>http://contact-
ednotes.sty.de.vu

###### Contents

  1. 1 Introductions
    1. 1.1 Introduction to versions $\textrm{v}<4$
    2. 1.2 Introduction to versions v4.00ff. (UL)
    3. 1.3 Availability
    4. 1.4 Introductory code
  2. 2 Put the line numbers to the lines
    1. 2.1 Basic code of lineno.sty \output
    2. 2.2 \LineNoTest
    3. 2.3 Other output routines (v4.2)
    4. 2.4 \MakeLineNo: Actually attach line number
  3. 3 Control line numbering
    1. 3.1 Inserting \output calls
    2. 3.2 Turning on/off
    3. 3.3 Display math
  4. 4 Line number references
    1. 4.1 Internals
    2. 4.2 The \linelabel command
  5. 5 The appearance of the line numbers
    1. 5.1 Basic code
    2. 5.2 Running line numbers
    3. 5.3 Pagewise line numbers
    4. 5.4 Twocolumn mode (New v3.06)
    5. 5.5 Numbering modulo $m$, starting at $f$
  6. 6 Package options
    1. 6.1 Extended referencing to line numbers. (v4.2)
    2. 6.2 \linelabel in math mode
    3. 6.3 Arrays, tabular environments (Revised v4.11)
    4. 6.4 Switch among settings
    5. 6.5 Compatibility with hyperref
    6. 6.6 A note on calling so many options
    7. 6.7 Execute options
  7. 7 Former package extensions
    1. 7.1 $displaymath$
    2. 7.2 Line numbers in internal vertical mode
    3. 7.3 Line number references with offset
    4. 7.4 Numbered quotation environments
    5. 7.5 Frame around a paragraph
  8. 8 Move \vadjust items (New v4.00)
    1. 8.1 Redefining \vadjust
    2. 8.2 Redefining the LaTeX commands
    3. 8.3 Reminder on obsoleteness
  9. 9 The final touch
  10. 10 The user commands
    1. 10.1 Customization hooks

##  1 Introductions

(New v4.00) Parts of former first section have been rendered separate
subsections for package version v4.00. (/New v4.00)

###  1.1 Introduction to versions $\textrm{v}<4$

This package provides line numbers on paragraphs. After TeX has broken a
paragraph into lines there will be line numbers attached to them, with the
possibility to make references through the LaTeX `\ref`, `\pageref` cross
reference mechanism. This includes four issues:

  * •

attach a line number on each line,

  * •

create references to a line number,

  * •

control line numbering mode,

  * •

count the lines and print the numbers.

The first two points are implemented through patches to the output routine.
The third by redefining `\par`, `\@par` and `\@@par`. The counting is easy, as
long as you want the line numbers run through the text. If they shall start
over at the top of each page, the aux-file as well as TeXs memory have to
carry a load for each counted line.

I wrote this package for my wife Petra, who needs it for transcriptions of
interviews. This allows her to precisely refer to passages in the text. It
works well together with `\marginpar`s, but not too well with displaymath.
`\footnote`s are a problem, especially when they are split, but we may get
there. (New v4.00 UL) Version v4.00 overcomes the problem, I believe. (/UL
/New v4.00)

lineno.sty works surprisingly well with other packages, for example,
`wrapfig.sty`. So please try if it works with whatever you need, and if it
does, please tell me, and if it does not, tell me as well, so I can try to fix
it.

###  1.2 Introduction to versions v4.00ff. (UL)

`lineno.sty` has been maintained by Stephan until version v3.14. From version
v4.00 onwards, maintenance is shifting towards Uwe Lück (UL), who is the
author of v4…code and of v4…changes in documentation. This came about as
follows.

Since late 2002, Christian Tapp and Uwe Lück have employed `lineno.sty` for
their `ednotes.sty`, a package supporting critical editions—cf.

http://ednotes.sty.de.vu

—while you find `ednotes.sty` and surrounding files in CTAN folder
/macros/latex/contrib/ednotes.

Soon, some weaknesses of `lineno.sty` showed up, mainly since Christian’s
critical editions (using `ednotes.sty`) needed lots of `\linelabel`s and
footnotes. (These weaknesses are due to weaknesses of LaTeX’s `\marginpar`
mechanism that Stephan used for `\linelabel`.) So we changed some `lineno.sty`
definitions in some extra files, which moreover offered new features. We sent
these files to Stephan, hoping he would take the changes into `lineno.sty`.
However, he was too short of time.

Writing a TUGboat article on Ednotes in 2004, we hoped to reduce the number of
files in the Ednotes bundle and so asked Stephan again. Now he generously
offered maintenance to me, so I could execute the changes on my own.

The improvements are as follows:

  * (i)

Footnotes placement approaches intentions better (footnotes formerly liked to
pile up at late pages).

  * (ii)

The number of `\linelabel`s in one paragraph is no longer limited to 18.

  * (iii)

`\pagebreak`, `\nopagebreak`, `\vspace`, and the star and optional versions of
`\\` work as one would expect (section 8).

  * (iv)

A command is offered which chooses the first line number to be printed in the
margin (subsection 5.5).

  * (v)

(New v4.1) LaTeX tabular environments (optionally) get line numbers as well,
and you can refer to them in the usual automatic way. (It may be considered a
shortcoming that, precisely, _rows_ are numbered, not lines.—See subsection
6.3.)

  * (vi)

We are moving towards referring to math items (subsection 6.2 and the hooks in
subsection 4.2). (/New v4.1)

(Thanks to Stephan for making this possible!)

Ednotes moreover profits from Stephan’s offer with regard to the documentation
of our code which yielded these improvements formerly. This documentation now
becomes printable, being part of the `lineno.sty` documentation.

Of course, Stephan’s previous `lineno.sty` versions were a great and ingenious
work and exhibit greatest TeXpertise. I never could have done this. I learnt a
lot in studying the code when Christian pointed out strange output results and
error messages, and there are still large portions of `lineno.sty` which I
don’t understand (consider only pagewise numbering of lines). Fortunately,
Stephan has offered future help if needed.—My code for attaching line numbers
to _tabular environments_ (as mentioned above, now still in `edtable.sty`)
developed from macros which Stephan and Christian experimented with in
December 2002. Stephan built the basics. (However, I then became too proud to
follow his advice only to use and modify `longtable.sty`.)

There are some issues concerning use of counters on which I don’t agree with
Stephan and where I would like to change the code if `lineno.sty` is “mine” as
Stephan offered. However, Stephan is afraid of compatibility problems from
which, in particular, his wife could suffer in the near future. So he demanded
that I change as little as possible for my first version. Instead of executing
changes that I plan I just offer my opinions at the single occasions. I hope
to get in touch this way with users who consider subtle features vital which I
consider strange.

On the other hand, the sections on improvements of the implementation have
been blown up very much and may be tiring and litte understandable for mere
_users_. These users may profit from the present presentation just by jumping
to sections 6 and 10. There is a user’s guide ulineno.tex which may be even
more helpful, but it has not been updated for a while.

###  1.3 Availability

In case you have found the present file otherwise than from CTAN: A recent
version and documentation of this package should be available from CTAN folder
/macros/latex/contrib/lineno. Or mail to one of the addresses at top of file.

###  1.4 Introductory code

This style option is written for LaTeX 2ε, November 1994 or later, since we
need the `\protected@write` macro.

(New v4.00) And we use `\newcommand*` for controlling length of user macro
arguments, which has been available since December 1994.

.3em

    \NeedsTeXFormat{LaTeX2e}[1994/12/01]
    \ProvidesPackage{lineno}
      [\filedate\space line numbers on paragraphs \fileversion]

(/New v4.00)

##  2 Put the line numbers to the lines

(New v4.00) This section contained the most basic package code previously. For
various purposes of version 4…, much of these basics have been to be modified.
Much of my (UL’s) reasoning on these modifications has been to be reported.
Sorry, the present section has been blown up awfully thus and contains
ramifications that may be difficult to trace. We add some `\subsection`
commands in order to cope with the new situation. (/New v4.00)

###  2.1 Basic code of lineno.sty \output

The line numbers have to be attached by the output routine. We simply set the
`\interlinepenalty` to $-100000$. The output routine will be called after each
line in the paragraph, except the last, where we trigger by `\par`. The
`\linenopenalty` is small enough to compensate a bunch of penalties (e.g.,
with `\samepage`).

(New v3.04) Longtable uses `\penalty`$-30000$. The lineno penalty range was
shrunk to $-188000\dots-32000$. (/New v3.04) (New v4.00) New values are listed
below (11111f.). (/New v4.00)

.3em

    \newcount\linenopenalty\linenopenalty=-100000

(UL) Hm. It is never needed below that this is a counter.
`\def\linenopenalty{-100000\relax}` would do. (I guess this consumes more
memory, but it is more important to save counters than to save memory.) I was
frightened by `-\linenopenalty` below, but indeed TeX interprets the string
`--100000` as 100000. Has any user or extension package writer ever called
`\linenopenalty=xxx`, or could I really change this?—The counter is somewhat
faster than the macro. Together with the compatibility question this seems to
support keeping the counter. (???) (/UL)

.3em

    \mathchardef\linenopenaltypar=32000

So let’s make a hook to `\output`, the direct way. The LaTeX macro
`\@reinserts` puts the footnotes back on the page.

(New v3.01) `\@reinserts` badly screws up split footnotes. The bottom part is
still on the recent contributions list, and the top part will be put back
there after the bottom part. Thus, since lineno.sty does not play well with
`\inserts` anyway, we can safely experiment with `\holdinginserts`, without
making things much worse.

Or that’s what I thought, but: Just activating `\holdinginserts` while doing
the `\par` will not do the trick: The `\output` routine may be called for a
real page break before all line numbers are done, and how can we get control
over `\holdinginserts` at that point?

Let’s try this: When the `\output` routine is run with `\holdinginserts=3` for
a real page break, then we reset `\holdinginserts` and restart `\output`.

Then, again, how do we keep the remaining `\inserts` while doing further line
numbers?

If we find `\holdinginserts`=$-3$ we activate it again after doing `\output`.
(/New v3.01)

(New v3.02) To work with multicol.sty, the original output routine is now
called indirectly, instead of being replaced. When multicol.sty changes
`\output`, it is a toks register, not the real thing. (/New v3.02)

(New v4.00) Two further complications are added.

  * (i)

Problems with footnotes formerly resulted from LaTeX’s `\@reinserts` in
`\@specialoutput` which Stephan’s `\linelabel` called via the `\marginpar`
mechanism.

  * (ii)

LaTeX commands using `\vadjust` formerly didn’t work as one would have hoped.
The problem is as follows: Printing the line number results from a box that
the output routine inserts at the place of the `\interlinepenalty`. `\vadjust`
items appear _above_ the `\interlinepenalty` (TeXbook p. 105). So
`\pagebreak`, e.g., formerly sent the line number to the next page, while the
penalty from `\nopagebreak` could not tie the following line, since it was
screened off by the line number box.—Our trick is putting the `\vadjust` items
into a list macro from which the output routine transfers them into the
vertical list, below the line number box.

In this case (ii), like in case (i), footnotes would suffer if
`\holdinginserts` were non-positive. Indeed, in both cases (i) and (ii) we
tackle the footnote problem by extending that part of Stephan’s output routine
that is active when `\holdinginserts` is positive. This extension writes the
line number `\newlabel` to the .aux file (which was formerly done under
$\verb~\holdinginserts~=-3$) and handles the `\vadjust` items.—To trigger
`\output` and its `\linelabel` or, resp., `\vadjust` part, the list of signal
penalties started immediately before is increased here (first for
`\linelabel`, second for postponed `\vadjust` items):

.3em

    \mathchardef\@Mllbcodepen=11111
    \mathchardef\@Mppvacodepen=11112

(/New v4.00) (New v4.2) David Kastrup urges to use a private name instead of
`\the\output` (LaTeX-L-list). Otherwise an `\output` routine loaded later and
using `\newtoks\output` again may get lost entirely. So we change use of
`\@LN@output`, using it for the former purpose. Reference to what appeared
with the name of `\output` here lasts for a few lines and then is given away.

.3em

    \let\@tempa\output
    \newtoks\output
    \let\@LN@output\output
    \output=\expandafter{\the\@tempa}

Now we add two cases to Stephan’s output routine. (New v4.00)

.3em

    \@tempa={%

(/New 4.2)

.3em

                \LineNoTest
                \if@tempswa

(New v4.00) We insert recognition of waiting `\linelabel` items—

.3em

                  \ifnum\outputpenalty=-\@Mllbcodepen
                    \WriteLineNo

—and of waiting `\vadjust` items:

.3em

                  \else
                    \ifnum\outputpenalty=-\@Mppvacodepen
                      \PassVadjustList
                    \else

(/New v4.00) (New v4.2) Outsource “Standard” output —which occurs so rarely—to
subsection 2.3:

.3em

                      \LineNoLaTeXOutput

(/New v4.2) (New v4.00) Two new `\fi`s for the `\linelabel` and `\vadjust`
tests—

.3em

                    \fi
                  \fi

—and the remaining is Stephan’s code again: (/New v4.00)

.3em

                \else
                  \MakeLineNo
                \fi
                }

(New v4.00) Our new macros `\WriteLineNo` and `\PassVadjustList` will be dealt
with in sections 4 and 8.1. (/New v4.00)

###  2.2 \LineNoTest

The float mechanism inserts `\interlinepenalty`s during `\output`. So
carefully reset it before going on. Else we get doubled line numbers on every
float placed in horizontal mode, e.g, from `\linelabel`.

Sorry, neither a `\linelabel` nor a `\marginpar` should insert a penalty, else
the following linenumber could go to the next page. Nor should any other
float. So let us suppress the `\interlinepenalty` altogether with the
`\@nobreak` switch.

Since (ltspace.dtx, v1.2p)[1996/07/26], the `\@nobreaktrue` does it’s job
globally. We need to do it locally here.

.3em

    \def\LineNoTest{%
      \let\@@par\@@@par
      \ifnum\interlinepenalty<-\linenopenaltypar
         \advance\interlinepenalty-\linenopenalty
         \@LN@nobreaktrue
         \fi
      \@tempswatrue
      \ifnum\outputpenalty>-\linenopenaltypar\else
         \ifnum\outputpenalty>-188000\relax
           \@tempswafalse
           \fi
         \fi
      }

    \def\@LN@nobreaktrue{\let\if@nobreak\iftrue} % renamed v4.33

(UL) I thought here were another case of the save stack problem explained in
TeXbook, p. 301, namely through both local and global changing `\if@nobreak`.
However, `\@LN@nobreak` is called during `\@LN@output` only, while
`\@nobreaktrue` is called by LaTeX’s `\@startsection` only. The latter never
happens during `\@LN@output`. So there is no local value of `\if@nobreak` on
save stack when `\@nobreaktrue` acts, since `\the\@LN@output` (where
`\@LN@output` is a new name for the original `\output`) is executed within a
group (TeXbook p. 21). (/UL)

###  2.3 Other output routines (v4.2)

I had thought of dealing with bad interference of footnotes (and
`\enlargethispage`) with (real) `\marginpar`s and floats _here_. Yet this is
done in

$\verb~http://~\mbox{[CTAN]}\verb~/macros/latex/contrib/tamefloats/tameflts.sty~$

now, and I prefer striving for compatibility with the latter. (See there for
expanding on the problem.) This requires returning the special absolute value
of `\holdinginserts` that `lineno.sty` finds at the end of a newly typeset
paragraph—now done in subsection 3.1 (`\linenumberpar`). The former
`\LineNoHoldInsertsTest` has been filled into here. Note: when the following
code is invoked, we have `\if@tempswa` = `\iftrue`. WARNING: I am still not
sure whether the present code is good for cooperating with other packages that
use `\holdinginserts`.

.3em

    \def\LineNoLaTeXOutput{%
      \ifnum \holdinginserts=\thr@@   % v4.33 without \@tempswafalse
        \global\holdinginserts-\thr@@
        \unvbox\@cclv
        \ifnum \outputpenalty=\@M \else \penalty\outputpenalty \fi
      \else
        \if@twocolumn \let\@makecol\@LN@makecol \fi
        \the\@LN@output % finally following David Kastrup’s advice.
        \ifnum \holdinginserts=-\thr@@
          \global\holdinginserts\thr@@ \fi
      \fi
    }

More on dealing with output routines from other packages: Since `lineno.sty`’s
output routine is called at least once for each output line, I think it should
be in TeX’s original `\output`, while output routines dealing with building
pages and with floats etc. should be filled into registers addressed by
`\output` after `\newtoks\output`. Therefore

  1. 1.

`tameflts.sty` should be loaded _after_ `lineno.sty`;

  2. 2.

if a class changes `\output` (APS journal class revtex4, e.g.), `lineno.sty`
should be loaded by `\RequirePackage` [here presumably following some options
in brackets]`{lineno}` _preceding_ `\documentclass`.

  3. 3.

If you actually maintain such a class, please consider loading `lineno.sty` on
some draft option. The bunch of lineno’s package options may be a problem, but
perhaps the purpose of your class is offering only very few of lineno’s
options anyway, maybe just one.

The latter may also be needed with classes that don’t follow David Kastrup’s
rule on changing `\output`.

###  2.4 \MakeLineNo: Actually attach line number

We have to return all the page to the current page, and add a box with the
line number, without adding breakpoints, glue or space. The depth of our line
number should be equal to the previous depth of the page, in case the page
breaks here, and the box has to be moved up by that depth.

The `\interlinepenalty` comes after the `\vadjust` from a `\linelabel`, so we
increment the line number _after_ printing it. The macro `\makeLineNumber`
produces the text of the line number, see section 5.

(UL) I needed a while to understand the sentence on incrementing. Correctly:
writing the `\newlabel` to the .aux file is triggered by the signal penalty
that `\end@float` inserts via `\vadjust`. However, this could be changed by
our new `\PostponeVadjust`. After `\c@linenumber` has been introduced as a
LaTeX counter, it might be preferable that it behaved like standard LaTeX
counters which are incremented shortly before printing. But this may be of
little practical relevance in this case, as `\c@linenumber` is driven in a
very non-standard way.—However still, this behaviour of `\c@linenumber`
generates a problem with our `edtable.sty`. (/UL).

Finally we put in the natural `\interlinepenalty`, except after the last line.

(New v3.10) Frank Mittelbach points out that box255 may be less deep than the
last box inside, so he proposes to measure the page depth with
`\boxmaxdepth=\maxdimen`. (/New v3.10)

(UL, New v4.00) We also resume the matter of `\vadjust` items that was started
in section 2.1.

TeX puts only nonzero interline penalties into the vertical list (TeXbook p.
105), while `lineno.sty` formerly replaced the signal interline penalty by
something closing with an explicit penalty of the value that the interline
penalty would have without `lineno.sty`. This is usually 0. Now, explicit
vertical penalties can be very nasty with respect to `\nopagebreak`, e.g., a
low (even positive) `\widowpenalty` may force a widow where you explicitly
tried to forbid it by `\nopagebreak` (see explanation soon below). The
`\nopagebreak` we create here would never work if all those zero penalties
were present.—On the other hand, we cannot just omit Stephan’s zero penalties,
because TeX puts a penalty of 10000 after what `lineno.sty` inserts (TeXbook
p. 125). This penalty must be overridden to allow page breaks between ordinary
lines. To revive `\nopagebreak`, we therefore replace those zero (or low)
penalties by penalties that the user demanded by `\nopagebreak`.—This
mechanism is not perfect and does not exactly restore the original LaTeX
working of `\pagebreak` and `\nopagebreak`. Viz., if there are several
vertical penalties after a line which were produced by closely sitting
`\[no]pagebreak`s, without `lineno.sty` the lowest penalty would be effective
(cf. TeXbook exercise 14.10). Our mechanism, by contrast, chooses the _last_
user-set penalty of the line as the effective one. It would not be very
difficult to come more close to the original mechanism, but until someone
urges us we will cling to the present simple way. You may consider an
advantage of the difference between our mechanism and the original one that
the user here can actually override low penalties by `\nopagebreak`, which may
be what a lay LaTeX user would expect. (/UL, /New v4.00)

.3em

    \def\MakeLineNo{%
       \@LN@maybe@normalLineNumber                        % v4.31
       \boxmaxdepth\maxdimen\setbox\z@\vbox{\unvbox\@cclv}%
       \@tempdima\dp\z@ \unvbox\z@
       \sbox\@tempboxa{\hb@xt@\z@{\makeLineNumber}}%

(New v4.00) Previously,

    %    \stepcounter{linenumber}%

followed. (Of course, there was no comment mark; I put it there to make
reading the actual code easy.)

(New v4.22: improved) Why not just

$\verb~\global\advance\c@linenumber\@ne~?$

`\stepcounter` additionally resets “subordinate” counters, but which could
these (usefully) be? Again, may be column counters with `edtable.sty`!?

But then, our `edtable.sty` and its `longtable` option should use it as well.
So use a shorthand supporting uniformity. You can even use it as a hook for
choosing `\global\advance\c@linenumber\@ne` instead of our choice. (/New
v4.22)

.3em

       \stepLineNumber

(New v4.4) Now

.3em

       \ht\@tempboxa\z@ \@LN@depthbox

appends the box containing the line number without changing `\prevdepth`—see
end of section. Now is the time for inserting the $\dots$ (/New v4.4)
`\vadjust` items. We cannot do this much later, because their right place is
above the artificial interline penalty which Stephan’s code will soon insert
(cf. TeXbook p. 105). The next command is just `\relax` if no `\vadjust` items
have been accumulated for the current line. Otherwise it is a list macro
inserting the `\vadjust` items and finally resetting itself. (This is made in
section 8.1 below.) If the final item is a penalty, it is stored so it can
compete with other things about page breaking.

.3em

       \@LN@do@vadjusts
       \count@\lastpenalty

At this place,

    %    \ifnum\outputpenalty=-\linenopenaltypar\else

originally followed. We need something _before_ the `\else`:

.3em

       \ifnum\outputpenalty=-\linenopenaltypar
         \ifnum\count@=\z@ \else

So final `\pagebreak[0]` or `\nopagebreak[0]` has no effect—but this will make
a difference after headings only, where nobody should place such a thing
anyway.

.3em

           \xdef\@LN@parpgbrk{%
             \penalty\the\count@
             \global\let\noexpand\@LN@parpgbrk
                          \noexpand\@LN@screenoff@pen}% v4.4

That penalty will replace former `\kern\z@` in `\linenumberpar`, see
subsection 3.1.—A few days earlier, I tried to send just a penalty value.
However, the `\kern\z@` in `\linenumberpar` is crucial, as I then found out.
See below.—The final penalty is repeated, but this does no harm. (It would not
be very difficult to avoid the repeating, but it may even be less efficient.)
It may be repeated due to the previous `\xdef`, but it may be repeated as well
below in the present macro where artificial interline penalty is to be
overridden.

.3em

         \fi
       \else

(/New v4.00)

.3em

         \@tempcnta\outputpenalty
         \advance\@tempcnta -\linenopenalty

(New v4.00)

    %        \penalty\@tempcnta

followed previously. To give `\nopagebreak` a chance, we do

.3em

         \penalty \ifnum\count@<\@tempcnta \@tempcnta \else \count@ \fi

instead.—In `linenox0.sty`, the `\else` thing once was omitted. Sergei
Mariev’s complaint (thanks!) showed that it is vital (see comment before
`\MakeLineNo`). The remaining `\fi` from previous package version closes the
`\ifnum\outputpenalty`…(/New v4.00)

.3em

       \fi
       }

(New v4.00)

.3em

    \newcommand\stepLineNumber{\stepcounter{linenumber}}

For reason, see use above. (/New v4.00)

(New v4.4) The depth preserving trick is drawn here from `\MakeLineNo` because
it will be used again in section 3.1.

.3em

    \def\@LN@depthbox{%
      \dp\@tempboxa=\@tempdima
      \nointerlineskip \kern-\@tempdima \box\@tempboxa}

(/New v4.4)

##  3 Control line numbering

###  3.1 Inserting \output calls

The line numbering is controlled via `\par`. LaTeX saved the TeX-primitive
`\par` in `\@@par`. We push it one level further out, and redefine `\@@par` to
insert the `\interlinepenalty` needed to trigger the line numbering. And we
need to allow pagebreaks after a paragraph.

New (2.05beta): the prevgraf test. A paragraph that ends with a displayed
equation, a `\noindent\par` or `wrapfig.sty` produce empty paragraphs. These
should not get a spurious line number via `\linenopenaltypar`.

.3em

    \let\@@@par\@@par
    \newcount\linenoprevgraf

(UL) And needs `\linenoprevgraf` to be a counter? Perhaps there may be a
paragraph having thousands of lines, so `\mathchardef` doesn’t suffice
(really??). A macro ending on `\relax` might suffice, but would be somewhat
slow. I think I will use `\mathchardef` next time. Or has any user used
`\linenoprevgraf`? (/UL)

.3em

    \def\linenumberpar{%
      \ifvmode \@@@par \else
        \ifinner \@@@par \else
          \xdef\@LN@outer@holdins{\the\holdinginserts}% v4.2
          \advance \interlinepenalty \linenopenalty
          \linenoprevgraf \prevgraf
          \global \holdinginserts \thr@@
          \@@@par
          \ifnum\prevgraf>\linenoprevgraf
            \penalty-\linenopenaltypar
          \fi

(New v4.00)

    %          \kern\z@

was here previously. What for? According to TeXbook p. 125, Stephan’s
interline penalty is changed into 10000. At the end of a paragraph, the
`\parskip` would follow that penalty of 10000, so there could be a page break
neither at the `\parskip` nor at the `\baselineskip` (TeXbook p. 110)—so there
could never be a page break between two paragraphs. So something must screen
off the 10000 penalty. Indeed, the `\kern` is a place to break. (Stephan once
knew this: see ‘allow pagebreaks’ above.)

Formerly, I tried to replace `\kern\z@` by

    %         \penalty\@LN@parpgpen\relax

—but this allows a page break after heading. So:

.3em

          \@LN@parpgbrk

These and similar changes were formerly done by `linenox1.sty`. (/New v4.00)

(New v4.4) A `\belowdisplayskip` may precede the previous when the paragraph
ends on a display-math; or there may be a `\topsep` from a list, etc.
`\addvspace` couldn’t take account for it with `\kern\z@` here. v4.32
therefore moved the space down – with at least two bad consequences. Moreover,
David Josef Dev observes that `\kern\z@` may inappropriately yield column
depth 0pt. For these reasons, we introduce `\@LN@screenoff@pen` below. (/New
v4.4)

.3em

          \global\holdinginserts\@LN@outer@holdins % v4.2
          \advance\interlinepenalty -\linenopenalty
        \fi     % from \ifinner ... \else
      \fi}      % from \ifvmode ... \else

(New v4.00, v4.4) Initialize `\@LN@parpgbrk`, accounting for earlier space and
for appropriate columndepth. We use former `\MakeLineNo`’s depth-preverving
trick `\@LN@depthbox` again:

.3em

    \def\@LN@screenoff@pen{%
      \ifdim\lastskip=\z@
        \@tempdima\prevdepth \setbox\@tempboxa\null
        \@LN@depthbox                           \fi}

    \global\let\@LN@parpgbrk\@LN@screenoff@pen

(/New v4.4, v4.00)

###  3.2 Turning on/off

The basic commands to enable and disable line numbers. `\@par` and `\par` are
only touched, when they are `\let` to `\@@@par`/`\linenumberpar`. The line
number may be reset to 1 with the star-form, or set by an optional argument
`[`$\langle$number$\rangle$`]`.

(New v4.00) We add `\ifLineNumbers` etc. since a number of our new adjustments
need to know whether linenumbering is active. This just provides a kind of
shorthand for `\ifx\@@par\linenumberpar`; moreover it is more stable: who
knows what may happen to `\@@par`?—A caveat: `\ifLineNumbers` may be wrong.
E.g., it may be `\iffalse` where it acts, while a `\linenumbers` a few lines
below—in the same paragraph—brings about that the line where the
`\ifLineNumbers` appears gets a marginal number. (New v4.3) Just noticed: Such
tricks have been disallowed with v4.11, see subsections 4.2 and 3.2.—Moreover,
the switching between meanings of `\linelabel` for a possible error message as
of v4.11 is removed. Speed is difficult to esteem and also depends on
applications. Just use the most simple code you find. (/New v4.3)

.3em

    \newif\ifLineNumbers \LineNumbersfalse

(/New v4.00)

.3em

    \def\linenumbers{%
         \LineNumberstrue                            % v4.00
         \xdef\@LN@outer@holdins{\the\holdinginserts}% v4.3

(New v4.3) The previous line is for `{linenomath}` in a first numbered
paragraph. (/New v4.3)

.3em

         \let\@@par\linenumberpar
     %      \let\linelabel\@LN@linelabel % v4.11, removed v4.3
         \ifx\@par\@@@par\let\@par\linenumberpar\fi
         \ifx\par\@@@par\let\par\linenumberpar\fi
         \@LN@maybe@moduloresume         % v4.31
         \@ifnextchar[{\resetlinenumber}%]
                     {\@ifstar{\resetlinenumber}{}}%
         }

    \def\nolinenumbers{%
      \LineNumbersfalse                              % v4.00
      \let\@@par\@@@par
     %   \let\linelabel\@LN@LLerror      % v4.11, removed v4.3
      \ifx\@par\linenumberpar\let\@par\@@@par\fi
      \ifx\par\linenumberpar\let\par\@@@par\fi
      }

(New v4.00) Moreover, it is useful to switch to `\nolinenumbers` in
`\@arrayparboxrestore`. We postpone this to section 8.2 where we’ll have an
appending macro for doing this. (/New v4.00)

What happens with a display math? Since `\par` is not executed, when breaking
the lines before a display, they will not get line numbers. Sorry, but I do
not dare to change `\interlinepenalty` globally, nor do I want to redefine the
display math environments here.

$display\ math$

See the subsection below, for a wrapper environment to make it work. But that
requires to wrap each and every display in your LaTeX source (see option
`displaymath` in subsections 6.4 and 7.1 for some relief [UL]).

The next two commands are provided to turn on line numbering in a specific
mode. Please note the difference: for pagewise numbering, `\linenumbers` comes
first to inhibit it from seeing optional arguments, since re-/presetting the
counter is useless.

.3em

    \def\pagewiselinenumbers{\linenumbers\setpagewiselinenumbers}
    \def\runninglinenumbers{\setrunninglinenumbers\linenumbers}

Finally, it is a LaTeX style, so we provide for the use of environments,
including the suppression of the following paragraph’s indentation.

(UL) I am drawing the following private thoughts of Stephan’s to publicity so
that others may think about them—or to remind myself of them in an efficient
way. (/UL)

    % TO DO: add \par to \linenumbers, if called from an environment.
    % To DO: add an \@endpe hack if \linenumbers are turned on
    %        in horizontal mode. {\par\parskip\z@\noindent} or
    %        something.

(UL) However, I rather think that `\linenumbers` and `\nolinenumbers` should
execute a `\par` already. (Then the `\par`s in the following definitions
should be removed.) (/UL)

.3em

    \@namedef{linenumbers*}{\par\linenumbers*}
    \@namedef{runninglinenumbers*}{\par\runninglinenumbers*}

    \def\endlinenumbers{\par\@endpetrue}
    \let\endrunninglinenumbers\endlinenumbers
    \let\endpagewiselinenumbers\endlinenumbers
    \expandafter\let\csname endlinenumbers*\endcsname\endlinenumbers
    \expandafter\let\csname endrunninglinenumbers*\endcsname\endlinenumbers
    \let\endnolinenumbers\endlinenumbers

###  3.3 Display math

Now we tackle the problem to get display math working. There are different
options.

  1. 1.

Precede every display math with a `\par`. Not too good.

  2. 2.

Change `\interlinepenalty` and associates globally. Unstable.

  3. 3.

Wrap each display math with a `{linenomath}` environment.

We’ll go for option 3. See if it works:

$display\ math$ (1)

The star form `{linenomath*}` should also number the lines of the display
itself,

$\displaystyle multi$ $\displaystyle line$ (2) $\displaystyle display$
$\displaystyle math$ (3) $\displaystyle\begin{array}[]{c}with\\\
array\end{array}$ (6)

including multline displays.

First, here are two macros to turn on linenumbering on paragraphs preceeding
displays, with numbering the lines of the display itself, or without. The
`\ifx..` tests if line numbering is turned on. It does not harm to add these
wrappers in sections that are not numbered. Nor does it harm to wrap a display
twice, e.q, in case you have some `{equation}`s wrapped explicitely, and later
you redefine `\equation` to do it automatically.

(New v4.3) To avoid the spurious line number above a display in vmode, I
insert `\ifhmode`. (/New v4.3)

.3em

    \newcommand\linenomathNonumbers{%
      \ifLineNumbers
        \ifnum\interlinepenalty>-\linenopenaltypar
          \global\holdinginserts\thr@@
          \advance\interlinepenalty \linenopenalty
         \ifhmode                                   % v4.3
          \advance\predisplaypenalty \linenopenalty
         \fi
        \fi
      \fi
      \ignorespaces
      }

    \newcommand\linenomathWithnumbers{%
      \ifLineNumbers
        \ifnum\interlinepenalty>-\linenopenaltypar
          \global\holdinginserts\thr@@
          \advance\interlinepenalty \linenopenalty
         \ifhmode                                   % v4.3
          \advance\predisplaypenalty \linenopenalty
         \fi
          \advance\postdisplaypenalty \linenopenalty
          \advance\interdisplaylinepenalty \linenopenalty
        \fi
      \fi
      \ignorespaces
      }

The `{linenomath}` environment has two forms, with and without a star. The
following two macros define the environment, where the stared/non-stared form
does/doesn’t number the lines of the display or vice versa.

.3em

    \newcommand\linenumberdisplaymath{%
      \def\linenomath{\linenomathWithnumbers}%
      \@namedef{linenomath*}{\linenomathNonumbers}%
      }

    \newcommand\nolinenumberdisplaymath{%
      \def\linenomath{\linenomathNonumbers}%
      \@namedef{linenomath*}{\linenomathWithnumbers}%
      }

    \def\endlinenomath{%
      \ifLineNumbers                            % v4.3
       \global\holdinginserts\@LN@outer@holdins % v4.21
      \fi
       \global % v4.21 support for LaTeX2e earlier than 1996/07/26.
       \@ignoretrue
    }
    \expandafter\let\csname endlinenomath*\endcsname\endlinenomath

The default is not to number the lines of a display. But the package option
`mathlines` may be used to switch that behavior.

.3em

    \nolinenumberdisplaymath

##  4 Line number references

###  4.1 Internals

The only way to get a label to a line number in a paragraph is to ask the
output routine to mark it.

(New v4.00) The following two paragraphs don’t hold any longer, see below.
(/New v4.00)

    % We use the marginpar mechanism to hook to ~\output~ for a
    % second time.  Marginpars are floats with number $-1$, we
    % fake marginpars with No $-2$. Originally, every negative
    % numbered float was considered to be a marginpar.
    %
    % The float box number ~\@currbox~ is used to transfer the
    % label name in a macro called ~\@LNL@~<box-number>.

A `\newlabel` is written to the aux-file. The reference is to
`\theLineNumber`, _not_ `\thelinenumber`. This allows to hook in, as done
below for pagewise line numbering.

(New v3.03) The `\@LN@ExtraLabelItems` are added for a hook to keep packages
like `{hyperref}` happy. (/New v3.03)

(New v4.00) We fire the `\marginpar` mechanism, so we leave LaTeX’s
`\@addmarginpar` untouched.

    % \let\@LN@addmarginpar\@addmarginpar
    % \def\@addmarginpar{%
    %    \ifnum\count\@currbox>-2\relax
    %      \expandafter\@LN@addmarginpar
    %    \else
    %      \@cons\@freelist\@currbox
    %      \protected@write\@auxout{}{%
    %          \string\newlabel
    %             {\csname @LNL@\the\@currbox\endcsname}%
    %             {{\theLineNumber}{\thepage}\@LN@ExtraLabelItems}}%
    %    \fi}

OK, we keep Stephan’s `\@LN@ExtraLabelItems`: (/New v4.00)

.3em

    \let\@LN@ExtraLabelItems\@empty

(New v4.00) We imitate the `\marginpar` mechanism without using the
`\@freelist` boxes. `\linelabel` will indeed place a signal penalty
(`\@Mllbcodepen`, new), and it will put a label into some list macro
`\@LN@labellist`. A new part of the output routine will take the labels from
the list and will write `\newlabel`s to the .aux file.

The following is a version of LaTeX’s `\@xnext`.

.3em

    \def\@LN@xnext#1\@lt#2\@@#3#4{\def#3{#1}\gdef#4{#2}}

This takes an item `#1` from a list `#4` into `#3`; to be used as
`\expandafter\@LN@xnext#4\@@#3#4`. Our lists use `\@lt` after each item for
separating. Indeed, there will be another list macro which can appear as
argument `#4`, this will be used for moving `\vadjust` items (section 8.1).
The list for `\linelabel`s is the following:

.3em

    \global\let\@LN@labellist\@empty

The next is the new part of the output routine writing the `\newlabel` to the
.aux file. Since it is no real page output, the page is put back to top of the
main vertical list.

.3em

    \def\WriteLineNo{%
      \unvbox\@cclv
      \expandafter \@LN@xnext \@LN@labellist \@@
                              \@LN@label \@LN@labellist
      \protected@write\@auxout{}{\string\newlabel{\@LN@label}%
             {{\theLineNumber}{\thepage}\@LN@ExtraLabelItems}}%
    }

(/New v4.00)

###  4.2 The \linelabel command

To refer to a place in line `\ref{`$\langle$foo$\rangle$`}` at page
`\pageref{`$\langle$foo$\rangle$`}` you place a
`\linelabel{`$\langle$foo$\rangle$`}` at that place.

demo ††margin:  See if it works: This paragraph starts on page LABEL:demo,
line LABEL:demo. (New v4.11)

    % If you use this command outside a ~\linenumbers~
    % paragraph, you will get references to some bogus
    % line numbers, sorry.  But we don’t disable the command,
    % because only the ~\par~ at the end of a paragraph  may
    % decide whether to print line numbers on this paragraph
    % or not.  A ~\linelabel~ may legally appear earlier than
    % ~\linenumbers~.

This trick is better not allowed—see subsections 4.2 and 3.2. (/New v4.11)

`\linelabel`

    %, via a fake float number $-2$, %% new mechanism v4.00

puts a `\penalty` into a `\vadjust`, which triggers the pagebuilder after
putting the current line to the main vertical list. A `\write` is placed on
the main vertical list, which prints a reference to the current value of
`\thelinenumber` and `\thepage` at the time of the `\shipout`.

A `\linelabel` is allowed only in outer horizontal mode. In outer vertical
mode we start a paragraph, and ignore trailing spaces (by fooling
`\@esphack`).

(New v4.00) We aim at relaxing the previous condition. We insert a hook
`\@LN@mathhook` and a shorthand `\@LN@postlabel` to support the `mathrefs`
option which allows `\linelabel` in math mode.

The next paragraph is no longer valid.

    % The argument of ~\linelabel~ is put into a macro with a
    % name derived from the number of the allocated float box.
    % Much of the rest is dummy float setup.

(/New v4.00)

(New v4.11)

    % \def\linelabel#1{%

I forgot `\linenumbers` today, costed me hours or so.

.3em

    \def\@LN@LLerror{\PackageError{lineno}{%
      \string\linelabel\space without \string\linenumbers}{%
      Just see documentation. (New feature v4.11)}\@gobble}

(New v4.3) Here some things have changed for v4.3. The previous `#1` has been
replaced by `\@gobble`. Ensuing, the `\linelabel` error message is re-
implemented. I find it difficult to compare efficiency of slight
alternatives—so choose an easy one. Explicit switching in `\linenumbers` and
`\nolinenumbers` is an additional command that may better be avoided.

.3em

    \newcommand\linelabel{%
      \ifLineNumbers \expandafter \@LN@linelabel
      \else          \expandafter \@LN@LLerror   \fi}

    \gdef\@LN@linelabel#1{%

`\gdef` for hyperref “symbolically”. (/New v4.11)

.3em

      \ifx\protect\@typeset@protect

$\leftarrow$ And a `\linelabel` should never be replicated in a mark or a TOC
entry. (/New v4.3)

.3em

       \ifvmode
           \ifinner \else
              \leavevmode \@bsphack \@savsk\p@
           \fi
       \else
           \@bsphack
       \fi
       \ifhmode
         \ifinner
           \@parmoderr
         \else

(New v4.00)

.3em

           \@LN@postlabel{#1}%

    %        \@floatpenalty -\@Mii
    %        \@next\@currbox\@freelist
    %            {\global\count\@currbox-2%
    %             \expandafter\gdef\csname @LNL@\the\@currbox\endcsname{#1}}%
    %            {\@floatpenalty\z@ \@fltovf \def\@currbox{\@tempboxa}}%
    %        \begingroup
    %            \setbox\@currbox \color@vbox \vbox \bgroup \end@float
    %        \endgroup
    %        \@ignorefalse \@esphack

(/New v4.00)

.3em

           \@esphack

(New v4.00) The `\@ignorefalse` was appropriate before because the `\@Esphack`
in `\end@float` set `\@ignoretrue`. Cf. LaTeX’s `\@xympar`. (/New v4.00)

.3em

         \fi
       \else

(New v4.00)

.3em

         \@LN@mathhook{#1}%

    %     \@parmoderr

Instead of complaining, you may just do your job. (/New v4.00)

.3em

       \fi
      \fi
       }

(New v4.00) The shorthand just does what happened with `linenox0.sty` before
`ednmath0.sty` (New v4.1: now `mathrefs` option) appeared, and the hook is
initialized to serve the same purpose. So errors come just where Stephan had
built them in, and this is just the LaTeX `\marginpar` behaviour.

.3em

    \def\@LN@postlabel#1{\g@addto@macro\@LN@labellist{#1\@lt}%
           \vadjust{\penalty-\@Mllbcodepen}}
    \def\@LN@mathhook#1{\@parmoderr}

(/New v4.00)

1

##  5 The appearance of the line numbers

###  5.1 Basic code

The line numbers are set as `\tiny\sffamily\arabic{linenumber}`, $10pt$ left
of the text. With options to place it right of the text, or . . .

. . . here are the hooks:

.3em

    \def\makeLineNumberLeft{%
      \hss\linenumberfont\LineNumber\hskip\linenumbersep}

    \def\makeLineNumberRight{%
      \linenumberfont\hskip\linenumbersep\hskip\columnwidth
      \hb@xt@\linenumberwidth{\hss\LineNumber}\hss}

    \def\linenumberfont{\normalfont\tiny\sffamily}

    \newdimen\linenumbersep
    \newdimen\linenumberwidth

    \linenumberwidth=10pt
    \linenumbersep=10pt

Margin switching requires `pagewise` numbering mode, but choosing the left or
right margin for the numbers always works.

.3em

    \def\switchlinenumbers{\@ifstar
        {\let\makeLineNumberOdd\makeLineNumberRight
         \let\makeLineNumberEven\makeLineNumberLeft}%
        {\let\makeLineNumberOdd\makeLineNumberLeft
         \let\makeLineNumberEven\makeLineNumberRight}%
        }

    \def\setmakelinenumbers#1{\@ifstar
      {\let\makeLineNumberRunning#1%
       \let\makeLineNumberOdd#1%
       \let\makeLineNumberEven#1}%
      {\ifx\c@linenumber\c@runninglinenumber
          \let\makeLineNumberRunning#1%
       \else
          \let\makeLineNumberOdd#1%
          \let\makeLineNumberEven#1%
       \fi}%
      }

    \def\leftlinenumbers{\setmakelinenumbers\makeLineNumberLeft}
    \def\rightlinenumbers{\setmakelinenumbers\makeLineNumberRight}

    \leftlinenumbers*

`\LineNumber` is a hook which is used for the modulo stuff. It is the command
to use for the line number, when you customize `\makeLineNumber`. Use
`\thelinenumber` to change the outfit of the digits.

We will implement two modes of operation:

  * •

numbers `running` through (parts of) the text

  * •

`pagewise` numbers starting over with one on top of each page.

Both modes have their own count register, but only one is allocated as a LaTeX
counter, with the attached facilities serving both.

.3em

    \newcounter{linenumber}
    \newcount\c@pagewiselinenumber
    \let\c@runninglinenumber\c@linenumber

Only the running mode counter may be reset, or preset, for individual
paragraphs. The pagewise counter must give a unique anonymous number for each
line.

(New v4.3) `\newcounter{linenumber}` was the only `\newcounter` in the whole
package, and formerly I was near using `\newcount` instead. Yet `\newcounter`
may be quite useful for `\includeonly`. It also supports resetting
“subcounters”, but what could these be? Well, `edtable` might introduce a
subcounter for columns. (Note that LaTeX’s setting commands would work with
`\newcount\c@linenumber` already, apart from this. And perhaps sometimes
`\refstepcounter{linenumber}` wouldn’t work—cf. my discussion of
`\stepcounter` in subsection 2.4, similarly `\refstep...` would be quite
useless. Even the usual redefinitions of `\thelinenumber` would work. It is
nice, on the other hand, that `\thelinenumber` is predefined here. LaTeX’s
initialization of the value perhaps just serves making clear LaTeX counters
should always be changed globally.—Shortened and improved the discussion
here.) (/New v4.3)

(New v4.22) `\c@linenumber` usually is—globally—incremented by `\stepcounter`
(at present), so resetting it locally would raise the save stack problem of
TeXbook p. 301, moreover it would be is useless, there is no hope of keeping
the values local (but see subsection 7.2). So I insert `\global`: (/New v4.22)

.3em

    \newcommand*\resetlinenumber[1][\@ne]{%
      \global                             % v4.22
      \c@runninglinenumber#1\relax}

(New v4.00)

    % \newcommand\resetlinenumber[1][1]{\c@runninglinenumber#1}

Added `\relax`, being quite sure that this does no harm and is quite
important, as with `\setcounter` etc. I consider this a bug fix (although
perhaps no user has ever had a problem with this). (/New v4.00)

(v4.22: I had made much fuss about resetting subordinate counters
here—removed, somewhat postponed.)

###  5.2 Running line numbers

Running mode is easy, `\LineNumber` and `\theLineNumber` produce
`\thelinenumber`, which defaults to `\arabic{linenumber}`, using the
`\c@runninglinenumber` counter. This is the default mode of operation.

.3em

    \def\makeRunningLineNumber{\makeLineNumberRunning}

    \def\setrunninglinenumbers{%
       \def\theLineNumber{\thelinenumber}%
       \let\c@linenumber\c@runninglinenumber
       \let\makeLineNumber\makeRunningLineNumber
       }

    \setrunninglinenumbers\resetlinenumber

###  5.3 Pagewise line numbers

Difficult, if you think about it. The number has to be printed when there is
no means to know on which page it will end up, except through the aux-file. My
solution is really expensive, but quite robust.

With version `v2.00` the hashsize requirements are reduced, because we do not
need one controlsequence for each line any more. But this costs some
computation time to find out on which page we are.

`\makeLineNumber` gets a hook to log the line and page number to the aux-file.
Another hook tries to find out what the page offset is, and subtracts it from
the counter `\c@linenumber`. Additionally, the switch `\ifoddNumberedPage` is
set true for odd numbered pages, false otherwise.

.3em

    \def\setpagewiselinenumbers{%
       \let\theLineNumber\thePagewiseLineNumber
       \let\c@linenumber\c@pagewiselinenumber
       \let\makeLineNumber\makePagewiseLineNumber
       }

    \def\makePagewiseLineNumber{\logtheLineNumber\getLineNumber
      \ifoddNumberedPage
         \makeLineNumberOdd
      \else
         \makeLineNumberEven
      \fi
      }

Each numbered line gives a line to the aux file

> `\@LN{`$\langle$line$\rangle$`}{`$\langle$page$\rangle$`}`

very similar to the `\newlabel` business, except that we need an arabic
representation of the page number, not what there might else be in `\thepage`.

.3em

    \def\logtheLineNumber{\protected@write\@auxout{}{%

(New v4.00) (UL) As Daniel Doherty observed, the earlier line

    %    \string\@LN{\the\c@linenumber}{\noexpand\the\c@page}}}

here may lead into an infinite loop when the user resets the page number
(think of `\pagenumbering`, e.g.). Stephan and I briefly discussed the matter
and decided to introduce a “physical”-page counter to which
`\logtheLineNumber` refers. It was Stephan’s idea to use `\cl@page` for
reliably augmenting the “physical”-page counter. However, this relies on the
output routine once doing `\stepcounter{page}`. Before Stephan’s suggestion, I
had thought of appending the stepping to LaTeX’s<EMAIL_ADDRESS>the macro
definition ends as follows.

.3em

       \string\@LN{\the\c@linenumber}{%

(New v4.2) The ‘truepage’ counter must start with `\c@` so it works with
`\include`, and the `\@addtoreset` below is needed for the same purpose.

.3em

         \noexpand\the\c@LN@truepage}}}

    \newcount\c@LN@truepage
    \g@addto@macro\cl@page{\global\advance\c@LN@truepage\@ne}
    \@addtoreset{LN@truepage}{@ckpt}

(/New v4.2) I had thought of offering more features of a LaTeX counter.
However, the user should better _not_ have access to this counter. `\c@page`
should suffice as a pagewise master counter.—To be sure, along the present
lines the user _can_ manipulate `\c@LN@truepage` by `\stepcounter{page}`.
E.g., she might do this in order to manually insert a photograph. Well, seems
not to harm.

The above usage of `\g@addto@macro` and `\cl@page` may be not as stable as
Stephan intended. His proposal used `\xdef` directly. But he used `\cl@page`
as well, and who knows … And as to `\g@addto@macro`, I have introduced it for
list macros anyway. (/UL) (/New v4.00)

From the aux-file we get one macro `\LN@P`$\langle$page$\rangle$ for each page
with line numbers on it. This macro calls four other macros with one argument
each. These macros are dynamically defined to do tests and actions, to find
out on which page the current line number is located.

We need sort of a pointer to the first page with line numbers, initiallized to
point to nothing:

.3em

    \def\LastNumberedPage{first}
    \def\LN@Pfirst{\nextLN\relax}

The four dynamic macros are initiallized to reproduce themselves in an `\xdef`

.3em

    \let\lastLN\relax  % compare to last line on this page
    \let\firstLN\relax % compare to first line on this page
    \let\pageLN\relax  % get the page number, compute the linenumber
    \let\nextLN\relax  % move to the next page

During the end-document run through the aux-files, we disable `\@LN`. I may
put in a check here later, to give a rerun recommendation.

.3em

    \AtEndDocument{\let\@LN\@gobbletwo}

Now, this is the tricky part. First of all, the whole definition of `\@LN` is
grouped, to avoid accumulation on the save stack. Somehow
`\csname`$\langle$cs$\rangle$`\endcsname` pushes an entry, which stays after
an `\xdef` to that $\langle$cs$\rangle$.

If `\LN@P`$\langle$page$\rangle$ is undefined, initialize it with the current
page and line number, with the _pointer-to-the-next-page_ pointing to nothing.
And the macro for the previous page will be redefined to point to the current
one.

If the macro for the current page already exists, just redefine the _last-
line-number_ entry.

Finally, save the current page number, to get the pointer to the following
page later.

.3em

    \def\@LN#1#2{{\expandafter\@@LN
                     \csname LN@P#2C\@LN@column\expandafter\endcsname
                     \csname LN@PO#2\endcsname
                     {#1}{#2}}}

    \def\@@LN#1#2#3#4{\ifx#1\relax
        \ifx#2\relax\gdef#2{#3}\fi
        \expandafter\@@@LN\csname LN@P\LastNumberedPage\endcsname#1%
        \xdef#1{\lastLN{#3}\firstLN{#3}%
                \pageLN{#4}{\@LN@column}{#2}\nextLN\relax}%
      \else
        \def\lastLN##1{\noexpand\lastLN{#3}}%
        \xdef#1{#1}%
      \fi
      \xdef\LastNumberedPage{#4C\@LN@column}}

The previous page macro gets its pointer to the current one, replacing the
`\relax` with the cs-token `\LN@P`$\langle$page$\rangle$.

.3em

    \def\@@@LN#1#2{{\def\nextLN##1{\noexpand\nextLN\noexpand#2}%
                    \xdef#1{#1}}}

Now, to print a line number, we need to find the page, where it resides. This
will most probably be the page where the last one came from, or maybe the next
page. However, it can be a completely different one. We maintain a cache,
which is `\let` to the last page’s macro. But for now it is initialized to
expand `\LN@first`, where the poiner to the first numbered page has been
stored in.

.3em

    \def\NumberedPageCache{\LN@Pfirst}

To find out on which page the current `\c@linenumber` is, we define the four
dynamic macros to do something usefull and execute the current cache macro.
`\lastLN` is run first, testing if the line number in question may be on a
later page. If so, disable `\firstLN`, and go on to the next page via
`\nextLN`.

.3em

    \def\testLastNumberedPage#1{\ifnum#1<\c@linenumber
          \let\firstLN\@gobble
      \fi}

Else, if `\firstLN` finds out that we need an earlier page, we start over from
the beginning. Else, `\nextLN` will be disabled, and `\pageLN` will run
`\gotNumberedPage` with four arguments: the first line number on this column,
the page number, the column number, and the first line on the page.

.3em

    \def\testFirstNumberedPage#1{\ifnum#1>\c@linenumber
         \def\nextLN##1{\testNextNumberedPage\LN@Pfirst}%
      \else
          \let\nextLN\@gobble
          \def\pageLN{\gotNumberedPage{#1}}%
      \fi}

We start with `\pageLN` disabled and `\nextLN` defined to continue the search
with the next page.

.3em

    \long\def \@gobblethree #1#2#3{}

    \def\testNumberedPage{%
      \let\lastLN\testLastNumberedPage
      \let\firstLN\testFirstNumberedPage
      \let\pageLN\@gobblethree
      \let\nextLN\testNextNumberedPage
      \NumberedPageCache
      }

When we switch to another page, we first have to make sure that it is there.
If we are done with the last page, we probably need to run TeX again, but for
the rest of this run, the cache macro will just return four zeros. This saves
a lot of time, for example if you have half of an aux-file from an aborted
run, in the next run the whole page-list would be searched in vain again and
again for the second half of the document.

If there is another page, we iterate the search.

.3em

    \def\testNextNumberedPage#1{\ifx#1\relax
         \global\def\NumberedPageCache{\gotNumberedPage0000}%
         \PackageWarningNoLine{lineno}%
                        {Linenumber reference failed,
          \MessageBreak  rerun to get it right}%
       \else
         \global\let\NumberedPageCache#1%
       \fi
       \testNumberedPage
       }

demo2 ††margin:  Let’s see if it finds the label on page LABEL:demo, line
LABEL:demo, and back here on page LABEL:demo2, line LABEL:demo2. To separate
the official hooks from the internals there is this equivalence, to hook in
later for whatever purpose:

.3em

    \let\getLineNumber\testNumberedPage

So, now we got the page where the number is on. We establish if we are on an
odd or even page, and calculate the final line number to be printed.

.3em

    \newif\ifoddNumberedPage
    \newif\ifcolumnwiselinenumbers
    \columnwiselinenumbersfalse

    \def\gotNumberedPage#1#2#3#4{\oddNumberedPagefalse
      \ifodd \if@twocolumn #3\else #2\fi\relax\oddNumberedPagetrue\fi
      \advance\c@linenumber\@ne
      \ifcolumnwiselinenumbers
         \subtractlinenumberoffset{#1}%
      \else
         \subtractlinenumberoffset{#4}%
      \fi
      }

You might want to run the pagewise mode with running line numbers, or you
might not. It’s your choice:

.3em

    \def\runningpagewiselinenumbers{%
      \let\subtractlinenumberoffset\@gobble
      }

    \def\realpagewiselinenumbers{%
      \def\subtractlinenumberoffset##1{\advance\c@linenumber-##1\relax}%
      }

    \realpagewiselinenumbers

For line number references, we need a protected call to the whole procedure,
with the requested line number stored in the `\c@linenumber` counter. This is
what gets printed to the aux-file to make a label:

.3em

    \def\thePagewiseLineNumber{\protect
           \getpagewiselinenumber{\the\c@linenumber}}%

And here is what happens when the label is refered to:

.3em

    \def\getpagewiselinenumber#1{{%
      \c@linenumber #1\relax\testNumberedPage
      \thelinenumber
      }}

A summary of all per line expenses:

CPU:

The `\output` routine is called for each line, and the page-search is done.

DISK:

One line of output to the aux-file for each numbered line

MEM:

One macro per page. Great improvement over v1.02, which had one control
sequence per line in addition. It blew the hash table after some five thousand
lines.

###  5.4 Twocolumn mode (New v3.06)

Twocolumn mode requires another patch to the `\output` routine, in order to
print a column tag to the .aux file.

.3em

    \AtBeginDocument{% v4.2, revtex4.cls (e.g.).
     % <- TODO v4.4+: Or better in \LineNoLaTeXOutput!?
      \let\@LN@orig@makecol\@makecol}
    \def\@LN@makecol{%
       \@LN@orig@makecol
       \setbox\@outputbox \vbox{%
          \boxmaxdepth \@maxdepth
          \protected@write\@auxout{}{%
              \string\@LN@col{\if@firstcolumn1\else2\fi}%
          }%
          \box\@outputbox
       }% \vbox
    } %% TODO cf. revtexln.sty.

    \def\@LN@col{\def\@LN@column} % v4.22, removed #1.
    \@LN@col{1}

###  5.5 Numbering modulo $m$, starting at $f$

Most users want to have only one in five lines numbered. `\LineNumber` is
supposed to produce the outfit of the line number attached to the line, while
`\thelinenumber` is used also for references, which should appear even if they
are not multiples of five.

(New v4.00) Moreover, some users want to control which line number should be
printed first. Support of this is now introduced here—see `\firstlinenumber`
below.—`numline.sty` by Michael Jaegermann and James Fortune offers
controlling which _final_ line numbers should not be printed. What is it good
for? We ignore this here until some user demands it.—Peter Wilson’s
`ledmac.sty` offers much different choices of line numbers to be printed, due
to Wayne Sullivan. (/New v4.00)

(New v4.22) `\c@linenumbermodulo` is rendered a fake counter, as discussed
since v4.00. So it can no longer be set by `\setcounter`. `\modulolinenumbers`
serves this purpose. Well, does anybody want to do what worked with
`\addtocounter`? (Then please tell me.)—At least, `\value` still works. For
the same purpose I rename the fake ‘firstlinenumber’ counter<EMAIL_ADDRESS>to
<EMAIL_ADDRESS>(/New v4.22)

    % \newcount\c@linenumbermodulo % removed for v4.22

(New v4.00)

`\themodulolinenumber` waits for being declared `\LineNumber` by
`\modulolinenumbers`. (This has been so before, no change.) Here is how it
looked before:

    % \def\themodulolinenumber{{\@tempcnta\c@linenumber
    %   \divide\@tempcnta\c@linenumbermodulo
    %   \multiply\@tempcnta\c@linenumbermodulo
    %   \ifnum\@tempcnta=\c@linenumber\thelinenumber\fi
    %   }}

(UL) This was somewhat slow. This arithmetic happens at every line. This time
I tend to declare an extra line counter (as opposed to my usual
recommendations to use counters as rarely as possible) which is stepped every
line. It could be incremented in the same way as `\c@LN@truepage` is
incremented via `\cl@page`! This is another point in favour of `{linenumber}`
being a LaTeX counter! When this new counter equals `\c@linenumbermodulo`, it
is reset, and `\thelinenumber` is executed.—It gets much slower by my support
of controlling the first line number below. I should improve this.—On the
other hand, time expense means very little nowadays, while the number of TeX
counters still is limited.

For the same purpose, moreover, attaching the line number box could be
intercepted earlier (in `\MakeLineNo`), without changing `\LineNumber`.
However, this may be bad for the latter’s announcement as a wizard interface
in section 10. (/UL)

Here is the new code. It is very near to my `lnopatch.sty` code which
introduced the first line number feature before.—I add starting with a
`\relax` which is so often recommended—without understanding this really. At
least, it will not harm.—Former group braces appear as
`\begingroup`/`\endgroup` here.

.3em

    \def\themodulolinenumber{\relax
      \ifnum\c@linenumber<\c@firstlinenumber \else
        \begingroup
          \@tempcnta\c@linenumber
          \advance\@tempcnta-\c@firstlinenumber
          \divide\@tempcnta\c@linenumbermodulo
          \multiply\@tempcnta\c@linenumbermodulo
          \advance\@tempcnta\c@firstlinenumber
          \ifnum\@tempcnta=\c@linenumber \thelinenumber \fi
        \endgroup
      \fi
    }

(/New v4.00)

The user command to set the modulo counter: (New v4.31) … a star variant is
introduced to implement Hillel Chayim Yisraeli’s idea to print the first line
number after an interruption of the edited text by some editor’s text,
regardless of the modulo. If it is 1, it is printed only with
`\firstlinenumber{1}`. I.e., you use `\modulolinenumbers*` for the new
feature, without the star you get the simpler behaviour that we have had so
far. And you can switch back from the refined behaviour to the simple one by
using `\modulolinenumbers` without the star.—This enhancement is accompanied
by a new package option `modulo*` which just executes `\modulolinenumbers*`
(subsection 6.4).—‘With `\firstlinenumber{1}`’ exactly means: ‘1’ is printed
if and only if the last `\firstlinenumber` before or in the paragraph that
follows the “interruption” has argument ‘1’ (or something _expanding_ to ‘1’,
or (to) something that TeX “reads” as 1, e.g.: a TeX count register storing
1).—At present, this behaviour may be unsatisfactory with pagewise line-
numbering $\dots$ I’ll make an experimental extra package if someone complains
…

.3em

    \newcommand\modulolinenumbers{%
      \@ifstar
        {\def\@LN@maybe@moduloresume{%
           \global\let\@LN@maybe@normalLineNumber
                                \@LN@normalLineNumber}%
                                           \@LN@modulolinenos}%
        {\let\@LN@maybe@moduloresume\relax \@LN@modulolinenos}%
    }

    \global\let\@LN@maybe@normalLineNumber\relax
    \let\@LN@maybe@moduloresume\relax
    \gdef\@LN@normalLineNumber{%
      \ifnum\c@linenumber=\c@firstlinenumber \else
        \ifnum\c@linenumber>\@ne
          \def\LineNumber{\thelinenumber}%
        \fi
      \fi

`\def` instead of `\let` enables taking account of a redefinition of
`\thelinenumber` in a present numbering environment (e.g.).

.3em

      \global\let\@LN@maybe@normalLineNumber\relax}

Instead of changing `\LineNumber` directly by `LN@moduloresume`, these tricks
enable `\modulolinenumbers*` to act as locally as I can make it. I don’t know
how to avoid that the output routine switches back to the normal modulo
behaviour by a global change. (An `\aftergroup` may fail in admittedly
improbable cases.)

.3em

    \newcommand*\@LN@modulolinenos[1][\z@]{%

The definition of this macro is that of the former `\modulolinenumbers`. (/New
v4.31)

.3em

      \let\LineNumber\themodulolinenumber
      \ifnum#1>\@ne
        \chardef                      % v4.22, note below
          \c@linenumbermodulo#1\relax
      \else\ifnum#1=\@ne

    %    \def\LineNumber{\thelinenumber}%

(New v4.00) I am putting something here to enable `\firstlinenumber` with
$\verb~\c@linenumbermodulo~=1$. With `lnopatch.sty`, a trick was offered for
this purpose. It is now obsolete.

.3em

        \def\LineNumber{\@LN@ifgreat\thelinenumber}%

(/New v4.00)

.3em

      \fi\fi
      }

(New v4.00) The default of `\@LN@ifgreat` is

.3em

    \let\@LN@ifgreat\relax

The previous changes as soon as `\firstlinenumber` is used:

.3em

    \newcommand*\firstlinenumber[1]{%
      \chardef\c@firstlinenumber#1\relax

No counter, little values allowed only—OK?—(UL) The change is local—OK? The
good thing is that `\global\firstlinenumber{`$\langle$number$\rangle$`}`
works. Moreover, `\modulolinenumbers` acts locally as well. (/UL)

(New v4.31)

.3em

      \let\@LN@ifgreat\@LN@ifgreat@critical}

    \def\@LN@ifgreat@critical{%
      \ifnum\c@linenumber<\c@firstlinenumber
        \expandafter \@gobble
      \fi}%

(/New v4.31)

The default value of `\c@firstlinenumber` is 0. This is best for what one
would expect from modulo printing.

.3em

    \let\c@firstlinenumber=\z@

For usage and effects of `\modulolinenumbers` and `\firstlinenumbers`, please
consult section 10. Two details on `\firstlinenumbers` here: (i)
`\firstlinenumber` acts on a paragraph if and only if (a) the paragraph is
broken into lines “in line-numbering mode” (after `\linenumbers`, e.g.); (b)
it is the last occurrence of a `\firstlinenumbers` before or in the paragraph.
(The practical applications of this that I can imagine don’t seem appealing to
me.) Cf. the explanation above of how `\modulolinenumbers` and
`\firstlinenumbers` interact—for this and for (ii), which is concerned with
possible arguments for `\firstlinenumbers`.

Note that the line numbers of the present section demonstrate the two devices.
(/New v4.00)

.3em

    \chardef\c@linenumbermodulo=5      % v4.2; ugly?
    \modulolinenumbers[1]

(New v4.22) The new implementation through `\chardef` decreases the
functionality and raises certain compatibility problems. I face this without
fear. The maximum modulo value is now `255`. I expect that this suffices for
usual applications. However, some users have “abused” `lineno.sty` to get
`ednotes.sty` features without line numbers, so have set the modulo to a value
beyond the total number of lines in their edition. This ought to be replaced
by `\let\makeLineNumber\relax`. (/New v4.22)

##  6 Package options

(New v4.1) The last heading formerly was the heading of what is now subsection
6.4. The options declared there were said to execute user commands only. This
was wrong already concerning `displaymath` and `hyperref`. At least, however,
these options were no or almost no occasion to skip definitions or
allocations. This is different with the options that we now insert.

###  6.1 Extended referencing to line numbers. (v4.2)

This subsection explains and declares package option `addpageno`.

If a line to whose number you refer by `\ref` is not on the present page, it
may be useful to add the number of the page on which the line occurs—and
perhaps it should not be added otherwise. In general, you could use the
Standard LaTeX package varioref for this. However, the latter usually produces
verbose output like ‘on the preceding page’— unless costumized—, while in
critical editions, e.g., one may prefer just adding the page number and some
mark on the left of the line number, irrespectively of how far the page is
apart etc. To support this, package option `addpageno` provides a command
`\vpagelineref` to be used in place of `\ref`. This produces, e.g., ‘34.15’
when referring to line 15 on page 34 while the present page is not 34. You can
customize the outcome, see the package file `vplref.sty` where the code and
further details are. You may conceive of `\vpagelineref` as a certain
customization of varioref’s `\vref`.

This implies that option `addpageno` requires the files `vplref.sty` and
`varioref.sty`. `addpageno` automatically loads both of them. Yet you can also
load `varioref.sty` on your own to use its package options.

Of course, you might better introduce a shorter command name for
`\vpagelineref` for your work, while we cannot predict here what shorthand
will fit your work. E.g., `\newcommand{\lref}{\vpagelineref}`.

If you really want to add the page number in _any_ case, use, e.g., some
`\myref` instead of `\ref`, after

$\verb~newcommand*{\myref}{\pageref{#1}.\ref{#1}}~$

or what you like. You don’t need the `addpageno` option in this case.

`addpageno` is due to a suggestion by Sergei Mariev.

.3em

    \DeclareOption{addpageno}{%
      \AtEndOfPackage{\RequirePackage{vplref}[2005/04/25]}}

###  6.2 \linelabel in math mode

We have made some first steps towards allowing `\linelabel` in math mode.
Because our code for this is presently experimental, we leave it to the user
to decide for the experiment by calling option `mathrefs`. We are in a hurry
now and thus leave the code, explanations, and discussion in the separate
package `ednmath0.sty`. Maybe we later find the time to improve the code and
move the relevant content of `ednmath0.sty` to here. The optimal situation
would be to define `\linelabel` from the start so it works in math mode,
omitting the `mathrefs` option.

Actually, this package even provides adjustments for analogously allowing
`ednotes.sty` commands in math mode. Loading the package is postponed to
`\AtBeginDocument` when we know whether these adjustments are needed.

.3em

    \DeclareOption{mathrefs}{\AtBeginDocument
      {\RequirePackage{ednmath0}[2004/08/20]}}

###  6.3 Arrays, tabular environments (Revised v4.11)

This subsection explains and declares package options `edtable`, `longtable`,
and `nolongtablepatch`.

The standard LaTeX tabular environments come as single boxes, so the
`lineno.sty` versions before v4.00 treated them as (parts of) single lines,
printing (at most) one line number beside each and stepping the line number
counter once only. Moreover, `\linelabel`s got lost. Of course, tables are
usually so high that you will want to treat each row like a line. (Christian
Tapp even desires that the lines of table entries belonging to a single row
are treated like ordinary lines.) Footnotes get lost in such environments as
well, which was bad for `ednotes.sty`.

We provide adjustments to count lines, print their numbers etc. as desired at
least for _some_ LaTeX tabular environments. (Like with other details, “some”
is to some extent explained in `edtable.sty`.) We do this similarly as with
option `mathrefs` before. We leave code and explanations in the separate
package `edtable.sty`. (For wizards: this package provides adjustments for
`ednotes.sty` as well. However, in the present case we don’t try to avoid them
unless `ednotes.sty` is loaded.) Package option `edtable` defines—by loading
`edtable.sty`—an environment `{edtable}` which is able to change some LaTeX
tabular environments with the desired effects. (v4.11: `edtable.sty` v1.3
counts LaTeX’s `{array}` [etc.] as a “tabular environment” as well.)

The `{edtable}` environment doesn’t help with `longtable.sty`, however. To
make up for this, `{longtable}` is adjusted in a different way—and this
happens only when another `lineno.sty` option `longtable` is called. In this
case, option `edtable` needn’t be called explicitly: option `longtable` works
as if `edtable` had been called.

Now, we are convinced that vertical spacing around `{longtable}` works
wrongly—see LaTeX bugs database tools/3180 and 3485, or see explanations in
the package `ltabptch.sty` (which is to be obtained from CTAN folder
/macros/latex/ltabptch). Our conviction is so strong that the `longtable`
option loads—after `longtable.sty`—the patch package `ltabptch.sty`. If the
user doesn’t want this (maybe preferring her own arrangement with the vertical
spacing), she can forbid it by calling `nolongtablepatch`.

The following code just collects some choices, which are then executed in
section 6.7. We use an `\if...` without `\newif` since `\if...true` and
`\if...false` would occur at most two times and only within the present
package. (`\AtEndOfClass{\RequirePackage{edtable}}` could be used instead, I
just overlooked this. Now I don’t change it because it allows to change the
version requirement at one place only.)

.3em

    \let\if@LN@edtable\iffalse

    \DeclareOption{edtable}{\let\if@LN@edtable\iftrue}

    \DeclareOption{longtable}{\let\if@LN@edtable\iftrue
      \PassOptionsToPackage{longtable}{edtable}}

    \DeclareOption{nolongtablepatch}{%
      \PassOptionsToPackage{nolongtablepatch}{edtable}}

(/New v4.1)

###  6.4 Switch among settings

There is a bunch of package options that execute user commands only.

Options `left` (`right`) put the line numbers on the left (right) margin. This
works in all modes. `left` is the default.

.3em

    \DeclareOption{left}{\leftlinenumbers*}

    \DeclareOption{right}{\rightlinenumbers*}

Option `switch` (`switch*`) puts the line numbers on the outer (inner) margin
of the text. This requires running the pagewise mode, but we turn off the page
offset subtraction, getting sort of running numbers again. The `pagewise`
option may restore true pagewise mode later.

.3em

    \DeclareOption{switch}{\setpagewiselinenumbers
                           \switchlinenumbers
                           \runningpagewiselinenumbers}

    \DeclareOption{switch*}{\setpagewiselinenumbers
                            \switchlinenumbers*%
                            \runningpagewiselinenumbers}

In twocolumn mode, we can switch the line numbers to the outer margin, and/or
start with number 1 in each column. Margin switching is covered by the
`switch` options.

.3em

    \DeclareOption{columnwise}{\setpagewiselinenumbers
                               \columnwiselinenumberstrue
                               \realpagewiselinenumbers}

The options `pagewise` and `running` select the major linenumber mechanism.
`running` line numbers refer to a real counter value, which can be reset for
any paragraph, even getting multiple paragraphs on one page starting with line
number one. `pagewise` line numbers get a unique hidden number within the
document, but with the opportunity to establish the page on which they finally
come to rest. This allows the subtraction of the page offset, getting the
numbers starting with 1 on top of each page, and margin switching in twoside
formats becomes possible. The default mode is `running`.

The order of declaration of the options is important here `pagewise` must come
after `switch`, to overide running pagewise mode. `running` comes last, to
reset the running line number mode, e.g, after selecting margin switch mode
for `pagewise` running. Once more, if you specify all three of the options
`[switch,pagewise,running]`, the result is almost nothing, but if you later
say `\pagewiselinenumbers`, you get margin switching, with real pagewise line
numbers.

.3em

    \DeclareOption{pagewise}{\setpagewiselinenumbers
                             \realpagewiselinenumbers}

    \DeclareOption{running}{\setrunninglinenumbers}

The option `modulo` causes only those linenumbers to be printed which are
multiples of five.

.3em

    \DeclareOption{modulo}{\modulolinenumbers\relax}

Option `modulo*` modifies `modulo` in working like `\modulolinenumbers*`—see
section 10.

.3em

    \DeclareOption{modulo*}{\modulolinenumbers*\relax}

The package option `mathlines` switches the behavior of the `{linenomath}`
environment with its star-form. Without this option, the `{linenomath}`
environment does not number the lines of the display, while the star-form
does. With this option, its just the opposite.

.3em

    \DeclareOption{mathlines}{\linenumberdisplaymath}

`displaymath` now calls for wrappers of the standard LaTeX display math
environment. This was previously done by `mlineno.sty`.

(New v4.3) Option ‘displaymath’ becomes default according to Erik Luijten’s
suggestion. I was finally convinced of this as soon as I discovered how to
avoid a spurious line number above `\begin{linenomath}` (subsection 3.3).
`\endlinenomath` provides `\ignorespaces`, so what could go wrong now?

.3em

    \DeclareOption{displaymath}{\PackageWarningNoLine{lineno}{%
                    Option [displaymath] is obsolete -- default now!}}

(/New v4.3)

###  6.5 Compatibility with hyperref

The `hyperref` package, via `nameref`, requires three more groups in the
second argment of a `\newlabel`. Well, why shouldn’t it get them? (New v3.07)
The presence of the `nameref` package is now detected automatically
`\AtBeginDocument`. (/New v3.07) (Fixed in v3.09) We try to be smart, and test
`\AtBeginDocument` if the `nameref` package is loaded, but `hyperref`
postpones the loading of `nameref` too, so this is all in vain.

(New v4.3) But we can also test at the first `\linelabel`. Regarding the
error-message for misplaced `\linelabel` from v4.11: previously,
`\linenumbers` rendered `\linelabel` the genuine version of `\linelabel` from
the start on. This doesn’t work now, since `\@LN@linelabel` may change its
meaning after the first `\linenumbers` and before a next one (if there is
some). (/New v4.3)

.3em

    \DeclareOption{hyperref}{\PackageWarningNoLine{lineno}{%
                    Option [hyperref] is obsolete.
      \MessageBreak The hyperref package is detected automatically.}}

    \AtBeginDocument{%
      \@ifpackageloaded{nameref}{%

(New v4.3) “Global” is merely “symbolic” `\AtBeginDoc...`. If `nameref` is not
detected here, the next `\@LN@linelabel` will do almost the same, then
globally indeed.

.3em

        \gdef\@LN@ExtraLabelItems{{}{}{}}%
      }{%
        \global\let\@LN@@linelabel\@LN@linelabel
        \gdef\@LN@linelabel{%

`\@ifpackageloaded` is “preamble only”, its—very internal—preamble definition
is replicated here:

.3em

         \expandafter
          \ifx\csname<EMAIL_ADDRESS>\else
            \gdef\@LN@ExtraLabelItems{{}{}{}}%
          \fi

Now aim at the “usual” behaviour:

.3em

          \global\let\@LN@linelabel\@LN@@linelabel
          \global\let\@LN@@linelabel\relax
          \@LN@linelabel
        }%
      }%
    }

(/New v4.3)

(New v4.1)

###  6.6 A note on calling so many options

The number of package options may stimulate worrying about how to _enter_ all
the options that one would like to use—they may not fit into one line.
Fortunately, you can safely break code lines after the commas separating the
option names in the `\usepackage` command (no comment marks needed).

###  6.7 Execute options

We stop declaring options and execute the ones that are called by the user.
(/New v4.1)

.3em

    \ProcessOptions

(New v4.1) Now we know whether `edtable.sty` is wanted and (if it is) with
which options it is to be called.

.3em

    \if@LN@edtable \RequirePackage{edtable}[2005/03/07] \fi

(/New v4.1)

##  7 Former package extensions

The extensions in this section were previously supplied in separate `.sty`
files.

###  7.1 $displaymath$

(New v4.3) From now on, you no longer need to type the `{linenomath}`
environment with the `\[`, `{equation}`, and `{eqnarray}` environments—and you
no longer need to use the former package option `displaymath` for this
feature. (/New v4.3)

The standard LaTeX display math environments are wrapped in a `{linenomath}`
environment.

(New 3.05) The `[fleqn]` option of the standard LaTeX classes defines the
display math environments such that line numbers appear just fine. Thus, we
need not do any tricks when `[fleqn]` is loaded, as indicated by presents of
the `\mathindent` register. (/New 3.05)

(New 3.05a) for `{eqnarray}`s we rather keep the old trick. (/New 3.05a)

(New 3.08) Wrap `\[` and `\]` into `{linenomath}`, instead of `{displaymath}`.
Also save the definition of `\equation`, instead of replicating the current
LaTeX definition. (/New 3.08)

.3em

     \@ifundefined{mathindent}{

      \let\LN@displaymath\[%
      \let\LN@enddisplaymath\]%
      \renewcommand\[{\begin{linenomath}\LN@displaymath}%
      \renewcommand\]{\LN@enddisplaymath\end{linenomath}}%

.3em

      \let\LN@equation\equation
      \let\LN@endequation\endequation
      \renewenvironment{equation}%
         {\linenomath\LN@equation}%
         {\LN@endequation\endlinenomath}%

     }{}% \@ifundefined{mathindent} -- 3rd arg v4.2, was \par!

      \let\LN@eqnarray\eqnarray
      \let\LN@endeqnarray\endeqnarray
      \renewenvironment{eqnarray}%
         {\linenomath\LN@eqnarray}%
         {\LN@endeqnarray\endlinenomath}%

(UL) Indeed. The LaTeX macros are saved for unnumbered mode, which is detected
by `\linenomath`. (/UL)

###  7.2 Line numbers in internal vertical mode

The command `\internallinenumbers` adds line numbers in internal vertical
mode, but with limitations: we assume fixed baseline skip.

(v4.22) v3.10 provided a global (`\global\advance`) as well as a local version
(star-form, using `\c@internallinenumber`). `\resetlinenumbers` acted locally
and was here used with the global version—save stack danger, TeXbook p. 301—in
v4.00 I disabled the global version therefore. Now I find that it is better to
keep a global version, and the now global `\resetlinenumbers` is perfect for
this. The global version allows continuing the “internal” numbers in the
ensuing “external” text, and—unless reset by brackets argument—continuing the
above series of line numbers. As with v3.10, the local version always starts
with line number one. A new `\@LN@iglobal` steps `\global`ly in the global
version, otherwise it is `\relax`. (I also remove all my stupid discussions as
of v4.00. And I use `\newcommand`.) (v4.22)

.3em

    \let\@LN@iglobal\global                           % v4.22

    \newcommand\internallinenumbers{\setrunninglinenumbers
         \let\@@par\internallinenumberpar
         \ifx\@par\@@@par\let\@par\internallinenumberpar\fi
         \ifx\par\@@@par\let\par\internallinenumberpar\fi
         \ifx\@par\linenumberpar\let\@par\internallinenumberpar\fi
         \ifx\par\linenumberpar\let\par\internallinenumberpar\fi
         \@ifnextchar[{\resetlinenumber}%]
                     {\@ifstar{\let\c@linenumber\c@internallinenumber
                               \let\@LN@iglobal\relax % v4.22
                               \c@linenumber\@ne}{}}%
         }

    \let\endinternallinenumbers\endlinenumbers
    \@namedef{internallinenumbers*}{\internallinenumbers*}
    \expandafter\let\csname endinternallinenumbers*\endcsname\endlinenumbers

    \newcount\c@internallinenumber
    \newcount\c@internallinenumbers

    \newcommand\internallinenumberpar{%
         \ifvmode\@@@par\else\ifinner\@@@par\else\@@@par
         \begingroup
            \c@internallinenumbers\prevgraf
            \setbox\@tempboxa\hbox{\vbox{\makeinternalLinenumbers}}%
            \dp\@tempboxa\prevdepth
            \ht\@tempboxa\z@
            \nobreak\vskip-\prevdepth
            \nointerlineskip\box\@tempboxa
         \endgroup
         \fi\fi
         }

    \newcommand\makeinternalLinenumbers{%
       \ifnum\c@internallinenumbers>\z@               % v4.2
       \hb@xt@\z@{\makeLineNumber}%
       \@LN@iglobal                                   % v4.22
         \advance\c@linenumber\@ne
       \advance\c@internallinenumbers\m@ne
       \expandafter\makeinternalLinenumbers\fi
       }
     % TODO v4.4+: star: line numbers right!? cf. lnocapt.sty

###  7.3 Line number references with offset

This extension defines macros to refer to line numbers with an offset, e.g.,
to refer to a line which cannot be labeled directly (display math). This was
formerly knows as `rlineno.sty`.

To refer to a pagewise line number with offset:

> `\linerefp[`$\langle$OFFSET$\rangle$`]{`$\langle$LABEL$\rangle$`}`

To refer to a running line number with offset:

> `\linerefr[`$\langle$OFFSET$\rangle$`]{`$\langle$LABEL$\rangle$`}`

To refer to a line number labeled in the same mode as currently selected:

> `\lineref[`$\langle$OFFSET$\rangle$`]{`$\langle$LABEL$\rangle$`}`

.3em

    \newcommand\lineref{%
      \ifx\c@linenumber\c@runninglinenumber
         \expandafter\linerefr
      \else
         \expandafter\linerefp
      \fi
    }

    \newcommand*\linerefp[2][\z@]{{%
       \let\@thelinenumber\thelinenumber
       \edef\thelinenumber{\advance\c@linenumber#1\relax
                           \noexpand\@thelinenumber}%
       \ref{#2}%
    }}

This goes deep into LaTeX’s internals.

.3em

    \newcommand*\linerefr[2][\z@]{{%
       \def\@@linerefadd{\advance\c@linenumber#1}%
       \expandafter\@setref\csname r@#2\endcsname
       \@linerefadd{#2}%
    }}

    \newcommand*\@linerefadd[2]{\c@linenumber=#1\@@linerefadd\relax
                                \thelinenumber}

###  7.4 Numbered quotation environments

The `{numquote}` and `{numquotation}` environments are like `{quote}` and
`{quotation}`, except there will be line numbers.

An optional argument gives the number to count from. A star `*` (inside or
outside the closing `}`) prevent the reset of the line numbers. Default is to
count from one.

(v4.22: A local version using `\c@internallinenumber` might be useful, see
subsection 7.2.)

.3em

    \newcommand\quotelinenumbers
       {\@ifstar\linenumbers{\@ifnextchar[\linenumbers{\linenumbers*}}}

    \newdimen\quotelinenumbersep
    \quotelinenumbersep=\linenumbersep
    \let\quotelinenumberfont\linenumberfont

    \newcommand\numquotelist
       {\leftlinenumbers
        \linenumbersep\quotelinenumbersep
        \let\linenumberfont\quotelinenumberfont
        \addtolength{\linenumbersep}{-\@totalleftmargin}%
        \quotelinenumbers
       }

    \newenvironment{numquote}     {\quote\numquotelist}{\endquote}
    \newenvironment{numquotation} {\quotation\numquotelist}{\endquotation}
    \newenvironment{numquote*}    {\quote\numquotelist*}{\endquote}
    \newenvironment{numquotation*}{\quotation\numquotelist*}{\endquotation}

###  7.5 Frame around a paragraph

The `{bframe}` environment draws a frame around some text, across page breaks,
if necessary.

This works only for plain text paragraphs, without special height lines. All
lines must be `\baselineskip` apart, no display math.

.3em

    \newenvironment{bframe}
      {\par
       \@tempdima\textwidth
       \advance\@tempdima 2\bframesep
       \setbox\bframebox\hb@xt@\textwidth{%
          \hskip-\bframesep
          \vrule\@width\bframerule\@height\baselineskip\@depth\bframesep
          \advance\@tempdima-2\bframerule
          \hskip\@tempdima
          \vrule\@width\bframerule\@height\baselineskip\@depth\bframesep
          \hskip-\bframesep
       }%
       \hbox{\hskip-\bframesep
             \vrule\@width\@tempdima\@height\bframerule\@depth\z@}%
       \nointerlineskip
       \copy\bframebox
       \nobreak
       \kern-\baselineskip
       \runninglinenumbers
       \def\makeLineNumber{\copy\bframebox\hss}%
      }
      {\par
       \kern-\prevdepth
       \kern\bframesep
       \nointerlineskip
       \@tempdima\textwidth
       \advance\@tempdima 2\bframesep
       \hbox{\hskip-\bframesep
             \vrule\@width\@tempdima\@height\bframerule\@depth\z@}%
      }

    \newdimen\bframerule
    \bframerule=\fboxrule

    \newdimen\bframesep
    \bframesep=\fboxsep

    \newbox\bframebox

##  8 Move \vadjust items (New v4.00)

This section completes reviving `\pagebreak`, `\nopagebreak`, `\vspace`, and
the star and optional form of `\\`. This was started in section 2.1 and
resumed in section 2.4 and subsection 3.1. The problem was explained in
section 2.1: `\vadjust` items come out at a bad position, and the LaTeX
commands named before work with `\vadjust` indeed. Our solution was sketched
there as well.

According to the caveat in subsection 3.2 concerning `\ifLineNumbers`, the
LaTeX commands enumerated may go wrong if you switch line numbering inside or
at the end of a paragraph.

###  8.1 Redefining \vadjust

`\vadjust` will temporarily be changed into the following command.

.3em

    \def\PostponeVadjust#1{%
      \global\let\vadjust\@LN@@vadjust

This undoes a `\global\let\vadjust\PostponeVadjust` which will start each of
the refined LaTeX commands. The `\global`s are most probably superfluous. They
might be useful should one `\vadjust` appear in a group starting after the
change of `\vadjust` into `\PostponeVadjust`. (UL) Even the undoing may be
superfluous, cf. discussion in section 8.2 below. (UL)

.3em

      \vadjust{\penalty-\@Mppvacodepen}%
      \g@addto@macro\@LN@vadjustlist{#1\@lt}%
    }
    \let\@LN@@vadjust\vadjust
    \global\let\@LN@vadjustlist\@empty
    \global\let\@LN@do@vadjusts\relax

These `\global`s are just to remind that all the changes of the strings after
`\let` should be `\global` (TeXbook p. 301). `\@LN@vadjustlist` collects the
`\vadjust` items of a paragraph. `\PassVadjustList` tears one `\vadjust` item
for the current line out of `\@LN@vadjustlist` and puts it into
`\@LN@do@vadjusts`. The latter is encountered each line in `\MakeLineNo`
(section 2.4), while those LaTeX `\vadjust` commands will come rather rarely.
So I decided that `\@LN@do@vadjust` is `\relax` until a `\vadjust` item is
waiting. In the latter case, `\@LN@do@vadjusts` is turned into a list macro
which resets itself to `\relax` when the other contents have been placed in
the vertical list.—`\PassVadjustList` is invoked by the output routine
(section 2.1), so the `\box255` must be put back.

.3em

    \def\PassVadjustList{%
      \unvbox\@cclv
      \expandafter \@LN@xnext \@LN@vadjustlist \@@
                              \@tempa \@LN@vadjustlist
      \ifx\@LN@do@vadjusts\relax
        \gdef\@LN@do@vadjusts{\global\let\@LN@do@vadjusts\relax}%
      \fi
      \expandafter \g@addto@macro \expandafter \@LN@do@vadjusts
        \expandafter {\@tempa}%
    }

###  8.2 Redefining the LaTeX commands

Now we change `\pagebreak` etc. so that they use `\PostponeVadjust` in place
of `\vadjust`. We try to do this as independently as possible of the
implementation of the LaTeX commands to be redefined. Therefore, we don’t just
copy macro definition code from any single implementation (say, latest LaTeX)
and insert our changes, but attach a conditional
`\global\let\vadjust\PostponeVadjust` to their left ends in a way which should
work rather independantly of their actual code. However, `\vadjust` should be
the primitive again after execution of the command. So the `\global\let...`
may be used only if it’s guaranteed that a `\vadjust` is near.—(UL) Sure? In
line numbering mode, probably each `\vadjust` coming from a LaTeX command
should be `\PostponeVadjust`. `\marginpar`s and floats seem to be the only
cases which are not explicitly dealt with in the present section. This would
be a way to avoid `\@LN@nobreaktrue`! Of course, the `\vadjust`s that the
present package uses then must be replaced by `\@LN@@vadjust`.—Maybe next
time. (/UL)

The next command and something else will be added to the LaTeX commands we are
concerned with here.

.3em

    \DeclareRobustCommand\@LN@changevadjust{%
      \ifvmode\else\ifinner\else
        \global\let\vadjust\PostponeVadjust
      \fi\fi
    }

(UL) What about math mode? Math display? Warn? (/UL)

`\@tempa` will now become a two place macro which adds first argument (single
token), enclosed by `\ifLineNumbers` …`\fi` to the left of second argument. As
long as we need it, we can’t use the star form of `\DeclareRobustCommand` or
the like, because AMS-LaTeX uses `\@tempa` for `\@ifstar`. (New v4.41) And for
the same reason, that `\CheckCommand*` had to be raised! (/New v4.41)

.3em

    \CheckCommand*\@parboxrestore{\@arrayparboxrestore\let\\\@normalcr}

    \def\@tempa#1#2{%
      \expandafter \def \expandafter#2\expandafter{\expandafter
        \ifLineNumbers\expandafter#1\expandafter\fi#2}%
    }

(UL) This `\ifLineNumber` can be fooled by `\linenumbers` ahead etc. It might
be better to place a signal penalty in any case and let the output routine
decide what to do. (/UL)

We use the occasion to switch off linenumbers where they don’t work anyway and
where we don’t want them, especially in footnotes:

.3em

    \@tempa\nolinenumbers\@arrayparboxrestore

We hope this suffices $\dots$ let’s check one thing at least: [(New v4.41) see
`\CheckCommand` above (/New v4.41)]

Now for the main theme of the section. The next lines assume that `\vspace`,
`\pagebreak`, and `\nopagebreak` use `\vadjust` whenever they occur outside
vertical mode; moreover, that they don’t directly read an argument. Indeed
`\pagebreak` and `\nopagebreak` first call something which tests for a left
bracket ahead, while `\vspace` first tests for a star.

.3em

    \@tempa\@LN@changevadjust\vspace
    \@tempa\@LN@changevadjust\pagebreak
    \@tempa\@LN@changevadjust\nopagebreak

`\\`, however, uses `\vadjust` only in star or optional form. We relax
independency of implementation in assuming that `\@normalcr` is the fragile
version of `\\` (and we use `\@ifstar`!). (Using a copy of `\\` would be
safer, but an ugly repetition of `\protect`.)

.3em

    \DeclareRobustCommand\\{%
      \ifLineNumbers
        \expandafter \@LN@cr
      \else
        \expandafter \@normalcr
      \fi
    }
    \def\@LN@cr{%
      \@ifstar{\@LN@changevadjust\@normalcr*}%
              {\@ifnextchar[{\@LN@changevadjust\@normalcr}\@normalcr}%
    }

Moreover we hope that `\newline` never leads to a `\vadjust`, although names
of some commands invoked by `\\` contain `newline`. At last, this seems to
have been OK since 1989 or even earlier.

0 Let’s have a few tests. Testing `\pagebreak` and `\nopagebreak` would be too
expensive here, but—oops!—we have just experienced a successful
`\vspace*{.5\baselineskip}`. A `\\*[.5\baselineskip]`
may look even more drastical, but this time we are happy about it. Note that
the line numbers have moved with the lines. Without our changes, one line
number would have “anticipated” the move of the next line, just as you can
observe it now. (/New v4.00)

###  8.3 Reminder on obsoleteness

(New v4.1) We have completed inclusion of the earlier extension packages
`linenox0.sty`, `linenox1.sty`, and `lnopatch.sty`. If one of them is loaded,
though, we produce an error message before something weird happens. We avoid
`\newif` because the switchings occur so rarely.

.3em

    \AtBeginDocument{%
      \let\if@LN@obsolete\iffalse
      \@ifpackageloaded{linenox0}{\let\if@LN@obsolete\iftrue}\relax
      \@ifpackageloaded{linenox1}{\let\if@LN@obsolete\iftrue}\relax
      \@ifpackageloaded{lnopatch}{\let\if@LN@obsolete\iftrue}\relax
      \if@LN@obsolete
        \PackageError{lineno}{Obsolete extension package(s)}{%
        With lineno.sty version 4.00 or later,\MessageBreak
        linenox0/linenox1/lnopatch.sty must no longer be loaded.}%
      \fi
    }

##  9 The final touch

There is one deadcycle for each line number.

.3em

    \advance\maxdeadcycles 100

    \endinput

##  10 The user commands

The user commands to turn on and off line numbering are

\linenumbers

Turn on line numbering in the current mode.

\linenumbers*

and reset the line number to 1.

\linenumbers[$\langle$number$\rangle$]

and start with $\langle$number$\rangle$.

\nolinenumbers

Turn off line numbering.

\runninglinenumbers*[$\langle$number$\rangle$]

Turn on `running` line numbers, with the same optional arguments as
`\linenumbers`. The numbers are running through the text over pagebreaks. When
you turn numbering off and on again, the numbers will continue, except, of
cause, if you ask to reset or preset the counter.

\pagewiselinenumbers

Turn on `pagewise` line numbers. The lines on each page are numbered beginning
with one at the first `pagewise` numbered line.

\resetlinenumber[$\langle$number$\rangle$]

Reset `[`Set`]` the line number to 1 `[`$\langle$number$\rangle$`]`.

\setrunninglinenumbers

Switch to `running` line number mode. Do _not_ turn it on or off.

\setpagewiselinenumbers

Switch to `pagewise` line number mode. Do _not_ turn it on or off.

\switchlinenumbers*

Causes margin switching in pagewise modes. With the star, put the line numbers
on the inner margin.

\leftlinenumbers*

\rightlinenumbers*

Set the line numbers in the left/right margin. With the star this works for
both modes of operation, without the star only for the currently selected
mode.

\runningpagewiselinenumbers

When using the pagewise line number mode, do not subtract the page offset.
This results in running line numbers again, but with the possibility to switch
margins. Be careful when doing line number referencing, this mode status must
be the same while setting the paragraph and during references.

\realpagewiselinenumbers

Reverses the effect of `\runningpagewiselinenumbers`.

\modulolinenumbers[$\langle$number$\rangle$]

Give a number only to lines which are multiples of
`[`$\langle$number$\rangle$`]`. If $\langle$number$\rangle$ is not specified,
the current value in the counter `linenumbermodulo` is retained.
$\langle$number$\rangle$=1 turns this off without changing `linenumbermodulo`.
The counter is initialized to 5.

\modulolinenumbers*[$\langle$number$\rangle$]

Like `\modulolinenumbers`, the only difference being that the first line
number after a `\linenumbers` (or `\runninglinenumbers`,
`\pagewiselinenumbers`, `\quotelinenumbers`) is printed regardless of the
modulo—yet ‘1’ is printed only after (or …) `\firstlinenumber{1}`. This also
applies to the first line of a `{linenumbers}` or respective environment. See
subsection 5.5 for another explanation. The behaviour may be unsatisfactory
with pagewise line-numbering.

\firstlinenumber

`\firstlinenumber{`$\langle$filino$\rangle$`}` brings about that (after it)
line numbers less than $\langle$filino$\rangle$ do _not_ appear in the margin.
Moreover, with `\modulolinenumbers[`$\langle$number$\rangle$`]`, just the line
numbers which are $\langle$filino$\rangle$ plus a multiple of
$\langle$number$\rangle$ are printed.—If you had
`\firstlinenumber{`$\langle$pos$\rangle$`}` with some
$\mbox{$\langle${pos}\/$\rangle$}>0$ and want to switch to printing multiples
of, e.g., 4, you best do `\modulolinenumbers[4]` and `\firstlinenumber{0}`.
(See subsection 5.5 for technical details.)

\linenumberdisplaymath

Number the lines of a display math in a `{linenomath}` environment, but do not
in a `{linenomath*}` environment. This is used by the package option
`[mathlines]`.

\nolinenumberdisplaymath

Do not Number the lines of a display math in a `{linenomath}` environment, but
do in a `{linenomath*}` environment. This is the default.

\linelabel

Set a `\linelabel{`$\langle$foo$\rangle$`}` to the line number where this
commands is in. Refer to it with the LaTeX referencing commands
`\ref{`$\langle$foo$\rangle$`}` and `\pageref{`$\langle$foo$\rangle$`}`.

The commands can be used globally, locally within groups or as environments.
It is important to know that they take action only when the `\par` is
executed. The `\end{`$\langle$mode$\rangle$`linenumbers}` commands provide a
`\par`. Examples:

> `{\linenumbers` $\langle$text$\rangle$ `\par}`
>
> `\begin{linenumbers}`
> $\langle$text$\rangle$
> `\end{linenumbers}`
>
> $\langle$paragraph$\rangle$ `{\linenumbers\par}`
>
> `\linenumbers`
> $\langle$text$\rangle$ `\par`
> `\nolinenumbers`
>
> `\linenumbers`
> $\langle$paragraph$\rangle$ `{\nolinenumbers\par}`
>

(New v4.00) However, the examples containing $\langle$paragraph$\rangle$ show
what you should _not_ do, at least if you use `\pagebreak`, `\nopagebreak`,
`\vspace`, `\\*` or `\\[`$\langle$space$\rangle$`]`—cf. section 8.

The same care should be applied to the “wizard” devices `\ifLineNumbers`
(subsection 3.2) and `\PostponeVadjust` (section 8.1). (/New v4.00)

(New v4.11) Oh, and the commands and environments of section s:Xt are missing.
Sorry, I am in a hurry now. May be next time.—And the environments
`{linenomath}` and `{linenomath*}`should get an own paragraph. In short, each
math display, equation, or `{eqnarray}` should be “wrapped” in one of
`{linenomath}` and `{linenomath*}`.

###  10.1 Customization hooks

There are several hooks to customize the appearance of the line numbers, and
some low level hooks for special effects.

\thelinenumber

This macro should give the representation of the line number in the LaTeX-
counter `linenumber`. The default is provided by LaTeX:

`\arabic{linenumber}`

\makeLineNumberLeft

This macro is used to attach a line number to the left of the text page. This
macro should fill an `\hbox to 0pt` which will be placed at the left margin of
the page, with the reference point aligned to the line to which it should give
a number. Please use the macro `\LineNumber` to refer to the line number.

The default definition is

`\hss\linenumberfont\LineNumber\hskip\linenumbersep`

\makeLineNumberRight

Like `\makeLineNumberLeft`, but for line numbers on the right margin.

The default definition is

`\linenumberfont\hskip\linenumbersep\hskip\textwidth`

`\hbox to\linenumberwidth{\hss\LineNumber}\hss`

\linenumberfont

This macro is initialized to

`\normalfont\tiny\sffamily`

\linenumbersep

This dimension register sets the separation of the linenumber to the text.
Default value is `10pt`.

\linenumberwidth

This dimension register sets the width of the line number box on the right
margin. The distance of the right edge of the text to the right edge of the
line number is `\linenumbersep` \+ `\linenumberwidth`. The default value is
`10pt`.

\theLineNumber

(for wizards)

This macro is called for printing a `\newlabel` entry to the aux-file. Its
definition depends on the mode. For running line numbers it’s just
`\thelinenumber`, while in pagewise mode, the page offset subtraction is done
in here.

\makeLineNumber

(for wizards)

This macro produces the line numbers. The definition depends on the mode. In
the running line numbers mode it just expands `\makeLineNumberLeft`.

\LineNumber

(for wizards)

This macro is called by `\makeLineNumber` to typeset the line number. This
hook is changed by the modulo mechanism and by `\firstlinenumber`.