Producing a table of contents that is both useful and aesthetic is one of the most difficult design problems in any work. Naturally, Eplain does not pretend to solve the design problem. Collecting the raw data for a table of contents, however, is much the same across documents. Eplain uses an auxiliary file with extension `.toc' (and the same root name as your document) to save the information.
To write an entry for the table of contents, you say
\writetocentry{part}{text},
where part is the type of part this entry is, e.g.,
`chapter', and text is the text of the title.
\writetocentry puts an entry into the .toc file that looks
like \tocpartentry{text}{page number}. The
text is written unexpanded.
A related command, \writenumberedtocentry, takes one additional
argument, the first token of which is expanded at the point of the
\writenumberedtocentry, but the rest of the argument is not
expanded. The usual application is when the parts of the document are
numbered. On the other hand, the one-level expansion allows you to use
the argument for other things as well (author's names in a proceedings,
say), and not have accents or other control sequences expanded. The
downside is that if you want full expansion of the third
argument, you don't get it--you must expand it yourself, before you
call \writenumberedtocentry.
For example:
\writenumberedtocentry{chapter}{A $\sin$ wave}{\the\chapno}
\writetocentry{section}{A section title}
Supposing \the\chapno expanded to `3' and that the
\write's occurred on pages eight and nine, respectively, the
above writes the following to the .toc file:
\tocchapterentry{A $\sin$ wave}{3}{8}
\tocsectionentry{A section title}{9}
You read the .toc file with the command \readtocfile.
Naturally, whatever \toc... entry commands that were written
to the file must be defined when \readtocfile is invoked. Eplain
has minimal definitions for \tocchapterentry,
\tocsectionentry, and \tocsubsectionentry, just to prevent
undefined control sequence errors in common cases. They aren't suitable
for anything but preliminary proofs.
After reading the .toc file, \readtocfile opens the file
for writing, thereby deleting the information from the previous run. You
should therefore arrange that \readtocfile be called
before the first call to a \writetoc... macro.
On the other hand, if you don't want to rewrite the .toc file,
perhaps because you are only running TeX on part of your manuscript,
you can set \rewritetocfilefalse.
By default, the `.toc' file has the root \jobname. If your
document has more than one contents--for example, if it is a collection
of papers, some of which have their own contents--you can tell Eplain
to use a different root name by defining the control sequence
\tocfilebasename.
In addition to the usual table of contents, you may want to have a list
of figures, list of tables, or other such contents-like list. You can do
this with \definecontentsfile{abbrev}. All of the
above commands are actually a special case that Eplain predefines with
\definecontentsfile{toc}
The abbrev is used both for the file extension and in the control sequence names.