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### 18.3 Raw Formatter Commands

The @if… conditionals just described must be used only with normal Texinfo source. For instance, most features of plain TeX will not work within @iftex. The purpose of @if… is to provide conditional processing for Texinfo source, not provide access to underlying formatting features. For that, Texinfo provides so-called raw formatter commands. They should only be used when truly required (most documents do not need them).

The first raw formatter command is @tex. 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. Texinfo processors will not output material in 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. If you need to make several definitions, you may wish to set \globaldefs=1 (its value will be restored to zero as usual when the group ends at @end tex, so it won’t cause problems with the rest of the document).

As an example, here is a displayed equation 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 a format not generated by TeX, you will not see the equation that appears in the printed manual.

Analogously, you can use @ifhtml … @end ifhtml to delimit Texinfo source 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 Texinfo source to be included in XML output only, and @xml … @end xml for a region of raw XML. Regions of raw text in other formats will also be present in the XML output, but with protection of XML characters and within corresponding elements. For example, the raw HTML text:

@html
<br />
@end html


will be included in the XML output as:

<html>
&lt;br /&gt;
</html>


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

The behavior of newlines in raw regions is unspecified.

In all cases, in raw processing, @ retains the same meaning as in the remainder of the document. Thus, the Texinfo processors must recognize and even execute, to some extent, the contents of the raw regions, regardless of the final output format. Therefore, specifying changes that globally affect the document inside a raw region leads to unpredictable and generally undesirable behavior. For example, using the @kbdinputstyle command inside a raw region is undefined.

The remedy is simple: don’t do that. Use the raw formatter commands for their intended purpose, of providing material directly in the underlying format. When you simply want to give different Texinfo specifications for different output formats, use the @if… conditionals and stay in Texinfo syntax.

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