@c Copyright (C) 1992, 93, 94 Karl Berry.
@c This is part of the Eplain manual.
@c For copying conditions, see the file eplain.texi.

@node Invoking Eplain
@chapter Invoking Eplain

@cindex Eplain, invoking
The simplest way to use Eplain is simply to put:

@example
\input eplain
@end example

@noindent 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 (@file{.fmt})
@pindex .fmt @r{file}
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 @code{&eplain} or @code{&etex} to @TeX{}'s @samp{**} prompt.
For example:

@example
initex
This is TeX, ...
**&eplain myfile
@end example

Depending on the implementation of @TeX{} which you are using, you might
also be able to invoke @TeX{} as @file{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 @code{\input eplain} will waste time; if it isn't, then you must
load it.  To solve this, Eplain defines the control sequence
@code{\eplain}
@findex eplain
to be the letter @code{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:
@example
\ifx\eplain\undefined \input eplain \fi
@end example
@noindent where @code{\undefined} must never acquire a definition.

Eplain consists of several source files:
@table @file
@item xeplain.tex
most of the macros;

@item arrow.tex
commutative diagram macros, @pxref{Arrow theoretic diagrams} (written by
Steven Smith);

@item btxmac.tex
bibliography-related macros, @pxref{Citations};

@item texnames.sty
abbreviations for various @TeX{}-related names, @pxref{Logos} (edited by
Nelson Beebe).

@end table

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

All of these files except @file{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 not
want to load them, to conserve @TeX{}'s memory.  Therefore, if the
control sequence @code{\nobibtex}
@findex nobibtex
is defined, then the bibliography definitions are skipped.  You must set
@code{\nobibtex} before @file{eplain.tex} is read, naturally.  For
example, you could start your input file like this:

@example
\let\nobibtex = t
\input eplain
@end example

By default, @code{\nobibtex} is undefined, and so the bibliography
definitions @emph{are} made.

@findex noarrow
Likewise, define @code{\noarrow} if you don't want to include the
commutative diagram macros from @file{arrow.tex}, perhaps because you
already have conflicting ones.

If you don't want to read or write an @file{aux} file at all, for any
kind of cross-referencing, define @code{\noauxfile}
@findex noauxfile
before reading @file{eplain.tex}.  This also turns off all warnings
about undefined labels.

@pindex amsppt.sty
@cindex AMS@TeX{} conflicts
Eplain conflicts with AMS@TeX{} (more precisely, with @file{amsppt.sty})
The macros @code{\cite} and @code{\ref} are defined by both.

If you want to use AMS@TeX{}'s @code{\cite}, the solution is to define
@code{\nobibtex} before reading Eplain, as described above.

If you have @file{amsppt.sty} loaded and use @code{\ref}, Eplain writes
a warning on your terminal. If you want to use the AMS@TeX{}
@code{\ref}, do @code{\let\ref = \amsref} after reading Eplain.
To avoid the warning, do @code{\let\ref = \eplainref} after reading
Eplain and before using @code{\ref}.
