17.3 Raw Formatter Commands

Inside a region delineated by @iftex and @end iftex, you can embed some raw TeX commands. The Texinfo processors will ignore such a region unless TeX output is being produced. You can write the TeX commands as you would write them in a normal TeX file, except that you must replace the ‘\’ used by TeX with an ‘@’. For example, in the @titlepage section of a Texinfo file, you can use the TeX command @vskip to format the copyright page. (The @titlepage command causes Info to ignore the region automatically, as it does with the @iftex command.)

However, most features of plain TeX will not work within @iftex, as they are overridden by Texinfo features. The purpose of @iftex is to provide conditional processing for the Texinfo source, not provide access to underlying formatting features.

You can enter plain TeX completely, and use ‘\’ in the TeX commands, by delineating a region with the @tex and @end tex commands. All plain TeX commands and category codes are restored within an @tex region. The sole exception is that the @ character still introduces a command, so that @end tex can be recognized properly. As with @iftex, Texinfo processors will ignore such a region unless TeX output is being produced.

In complex cases, you may wish to define new TeX macros within @tex. You must use \gdef to do this, not \def, because @tex regions are processed in a TeX group.

As an example, here is a mathematical expression written in plain TeX:

@tex
$$ \chi^2 = \sum_{i=1}^N
         \left (y_i - (a + b x_i)
         \over \sigma_i\right)^2 $$
@end tex

The output of this example will appear only in a printed manual. If you are reading this in Info, you will not see the equation that appears in the printed manual.

Analogously, you can use @ifhtml … @end ifhtml to delimit a region to be included in HTML output only, and @html … @end html for a region of raw HTML.

Likewise, you can use @ifxml … @end ifxml to delimit a region to be included in XML output only, and @xml … @end xml for a region of raw XML.

Again likewise, you can use @ifdocbook … @end ifdocbook to delimit a region to be included in Docbook output only, and @docbook … @end docbook for a region of raw Docbook.

In all cases, the exception to the raw processing is that @ is still an escape character, so the @end command can be recognized.