Invoking Eplain
***************

The simplest way to use Eplain is simply to put:

     \input eplain

at the beginning of your input file.  The macro file is small enough that reading it does not take an unbearably long time---at least on contemporary machines.

In addition, if a format (.fmt) file has been created for Eplain (see the previous section), you can eliminate the time spent reading the macro source file.  You do this by responding &eplain or &etex to TeX's ** prompt. For example:

     initex
     This is TeX, ...
     **&eplain myfile

Depending on the implementation of TeX which you are using, you might also be able to invoke TeX as etex and have the format file automatically read.

If you write something which you will be distributing to others, you won't know if the Eplain format will be loaded already.  If it is, then doing \input eplain will waste time; if it isn't, then you must load it.  To solve this, Eplain defines the control sequence \eplain to be the letter t (a convention borrowed from Lisp; it doesn't actually matter what the definition is, only that the definition exists).  Therefore, you can do the following:

     \ifx\eplain\undefined \input eplain \fi

where \undefined must never acquire a definition.

Eplain consists of several source files:

xeplain.tex
     most of the macros;

arrow.tex
     commutative diagram macros, see Arrow theoretic diagrams (written by Steven Smith);

btxmac.tex
     bibliography-related macros, see Citations;

texnames.sty
     abbreviations for various TeX-related names, see Logos (edited by Nelson Beebe).

The file eplain.tex is all of these files merged together, with comments removed.

All of these files except xeplain.tex can be input individually, if all you want are the definitions in that file.

Also, since the bibliography macros are fairly extensive, you might to not load them, while loading the rest of Eplain, to conserve memory in TeX.  Therefore, you can control whether or not eplain.tex defines the bibliography-related stuff when you run TeX: if the control sequence \nobibtex is defined, then the definitions aren't made.  You must set \nobibtex before eplain.tex is read, naturally.  For example, you could start your input file like this:

     \let\nobibtex = t
     \input eplain

By default, \nobibtex is undefined, and so the bibliography definitions are made.

Sometimes you may want to be even more drastic than \nobibtex---not read or write an aux file at all, for any kind of cross-referencing.  This happens if you define \noauxfile before reading eplain.tex.  This also turns off all warnings about undefined labels.