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diff --git a/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-protect.html b/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-protect.html index 710c346f896..dd0389f9118 100644 --- a/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-protect.html +++ b/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-protect.html @@ -4,15 +4,13 @@ <h3>What’s the reason for ‘protection’?</h3> <p/>Sometimes LaTeX saves data it will reread later. These data are often the argument of some command; they are the so-called moving -arguments. (‘Moving’ because data are moved around.) Places to look for +arguments. (‘Moving’ because data are moved around.) Candidates are all arguments that may go into table of contents, list of figures, <em>etc</em>.; namely, data that are written to an auxiliary file and read in later. Other places are those data that might appear in head- or footlines. Section headings and figure captions are the most prominent examples; there’s a complete list in Lamport’s book (see <a href="FAQ-books.html">TeX-related books</a>). -<p/> - <p/>What’s going on really, behind the scenes? The commands in moving arguments are normally expanded to their internal structure during the process of saving. Sometimes this expansion results in invalid TeX @@ -26,26 +24,62 @@ illegal TeX code during the save process. TeX code during the save process. <p/>Lamport’s book says in its description of every LaTeX command whether it is ‘robust’ or ‘fragile’; it also says that every command with an -optional argument is fragile. These lists aren’t as reliable as the -list of moving arguments; the statements may have been true in -early versions of LaTeX2e but are not any longer necessarily so: +optional argument is fragile. The list isn’t reliable, and neither +is the assertion about optional arguments; the statements may have +been true in early versions of LaTeX2e but are not any longer +necessarily so: <ul> <li> Some fragile commands, such as <code>\</code><code>cite</code>, have been made robust in later revisions of LaTeX. -<li> Some robust commands are redefined by certain packages to be - fragile (the <code>\</code><code>cite</code> command commonly suffers this treatment). <li> Some commands, such as <code>\</code><code>end</code> and <code>\</code><code>nocite</code>, are fragile even though they have no optional arguments. <li> The “user’s way” of creating a command with an optional - argument (using <code>\</code><code>newcommand</code>) now always creates a robust - command. There is no reason that a package author should not also - make robust commands with optional arguments as part of the - package. + argument (using <code>\</code><code>newcommand</code> or <code>\</code><code>newcommand*</code>) now always + creates a robust command (though macros without optional arguments + may still be fragile if they do things that are themselves fragile). +<li> There is no reason that a package author should not also make + robust commands with optional arguments as part of the package. +<li> Some robust commands are redefined by certain packages to be + fragile (the <code>\</code><code>cite</code> command commonly suffers this treatment). </ul> -In short, the situation is confusing. No-one believes this is -satisfactory, and the LaTeX team have removed the need for +Further, simply “hiding” a fragile command in another command, has +no effect on fragility. So, if <code>\</code><code>fred</code> is fragile, and you write: +<blockquote> +<pre> +\newcommand{\jim}{\fred} +</pre> +</blockquote><p> +then <code>\</code><code>jim</code> is fragile too. There is, however, the +<code>\</code><code>newcommand</code>-replacement <code>\</code><code>DeclareRobustCommand</code>, which +<em>always</em> creates a robust command (whether or not it has optional +arguments). The syntax of <code>\</code><code>DeclareRobustCommand</code> is substantially +identical to that of <code>\</code><code>newcommand</code>, and if you do the wrapping +trick above as: +<blockquote> +<pre> +\DeclareRobustCommand{\jim}{\fred} +</pre> +</blockquote><p> +then <code>\</code><code>jim</code> is robust. +<p/>Finally, we have the <i>makerobust</i> package, which defines +<code>\</code><code>MakeRobustCommand</code> to convert a command to be robust. With the +package, the “wrapping” above can simply be replaced by: +<blockquote> +<pre> +\MakeRobustCommand\fred +</pre> +</blockquote><p> +Whereafter, <code>\</code><code>fred</code> is robust. Using the package may be reasonable +if you have lots of fragile commands that you need to use in moving +arguments. +<p/>In short, the situation is confusing. No-one believes this is +satisfactory; the LaTeX team have removed the need for protection of some things, but the techniques available in current LaTeX mean that this is an expensive exercise. It remains a long-term aim of the team to remove all need for <code>\</code><code>protect</code>ion. +<dl> +<dt><tt><i>makerobust.sty</i></tt><dd>Distributed with Heiko Oberdiek’s packages + <a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/oberdiek.zip">macros/latex/contrib/oberdiek</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/oberdiek.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/oberdiek/">browse</a>) +</dl> <p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=protect">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=protect</a> </body> |