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diff --git a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-patch.html b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-patch.html deleted file mode 100644 index 38193d85b47..00000000000 --- a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-patch.html +++ /dev/null @@ -1,122 +0,0 @@ -<head> -<title>UK TeX FAQ -- question label patch</title> -</head><body> -<h3>Patching existing commands</h3> -<p/>In the general case (possibly sticking something in the middle of an -existing command) this is difficult. However, the common requirement, -to add some code at the beginning or the end of an existing command, -is conceptually quite easy. Suppose we want to define a version of a -command that does some small extension of its original definition: we -would naturally write: -<blockquote> -<pre> -\renewcommand{\splat}{\mumble\splat} -</pre> -</blockquote><p> -However, this would not work: a call to <code>\</code><code>splat</code> would execute -<code>\</code><code>mumble</code>, and the call the redefined <code>\</code><code>splat</code> again; this is an -unterminated recursion, that will quickly exhaust TeX’s memory. -<p/>Fortunately, the TeX primitive <code>\</code><code>let</code> command comes to our -rescue; it allows us to take a “snapshot” of the current state of a -command, which we can then use in the redefinition of the command. -So: -<blockquote> -<pre> -\let\OldSmooth\smooth -\renewcommand{\smooth}{\mumble\OldSmooth} -</pre> -</blockquote><p> -effects the required patch, safely. Adding things at the end of a -command works similarly. If <code>\</code><code>smooth</code> takes arguments, one must -pass them on: -<blockquote> -<pre> -\let\OldSmooth\smooth -\renewcommand{\smooth}[2]{\mumble\OldSmooth{#1}{#2}} -</pre> - -</blockquote><p> -<p/>The general case may be achieved in two ways. First, one can use the -LaTeX command <code>\</code><code>CheckCommand</code>; this compares an existing command -with the definition you give it, and issues a warning if two don’t -match. Use is therefore: -<blockquote> - <code>\CheckCommand{\complex}{</code><<i>original definition</i>><code>}</code><br> - <code>\renewcommand{\complex}{</code><<i>new definition</i>><code>}</code> -</blockquote><p> -This technique is obviously somewhat laborious, but if the original -command comes from a source that’s liable to change under the control -of someone else, it does at least warn you that your patch is in -danger of going wrong. -<p/>Otherwise, LaTeX users may use one of the <i>patchcmd</i>, -<i>ted</i> or <i>etoolbox</i> packages. -<p/>The <i>patchcmd</i> package addresses a slightly simpler task, by -restricting the set of commands that you may patch; you mayn’t patch -any command that has an optional argument, though it does deal with -the case of commands defined with <code>\</code><code>DeclareRobustCommand</code>. The -package defines a <code>\</code><code>patchcommand</code> command, that takes three -arguments: the command to patch, stuff to stick at the front of its -definition, and stuff to stick on the end of its definition. So, -after -<blockquote> -<pre> -\def\b{b} -\patchcmd\b{a}{c} -</pre> -</blockquote><p> -we will have a new version of <code>\</code><code>b</code> defined as “<code>abc</code>”. -<p/>The <i>ted</i> package is a ‘token list editor’, and provides a -command <code>\</code><code>substitute</code> which will patch the -contents of a macro, putting the result in a token-list, or -(in the form <code>\</code><code>Substitute*</code>) using the result to (re)define a -macro. The following example defines a simple macro, and then changes -its definition: -<blockquote> -<pre> -\newcommand{\myfont}% - {\Large\sffamily\selectfont} -\Substitute*[\renewcommand{\myfont}]{\myfont}% - {\Large\sffamily}{\huge\itshape} -</pre> -</blockquote><p> -The macro’s definition is now: -<blockquote> -<pre> -\huge\itshape\selectfont -</pre> -</blockquote><p> -<p/>The package also offers a command <code>\</code><code>ShowTokens</code>, which shows the -content of its argument, one token to a line, with details of the -token’s category code, etc. This is recommended as a debugging tool. -<p/>The <i>etoolbox</i> (which provides user access to e-TeX’s -programming facilities) provides a command <code>\</code><code>patchcmd</code> which is -very similar to <code>\</code><code>Substitute</code>, except that it only replaces a -single instance of the token(s) in its search pattern. Since not all -commands may be patched in this way, <code>\</code><code>patchcmd</code> takes extra -arguments for <em>success</em> and <em>failure</em> cases. The -package also provides commands that prepend (<code>\</code><code>pretocmd</code>) or append -(<code>\</code><code>apptocmd</code>) to the definition of a command. Not all commands may -be patched in this way; the package provides a command -<code>\</code><code>ifpatchable</code> which checks the prerequisites, and checks that the -target command’s body does indeed include the patch string you propose -to use. (The command <code>\</code><code>ifpatchable*</code> omits the test on the patch -string.) -<p/>Finally, we’ll briefly consider a package that is (just about) -usable, but not really recommendable. <i>Patch</i> gives you an -ingenious (and difficult to understand) mechanism, and comes as an -old-style LaTeX documented macro file, which can no longer be -processed to <a href="FAQ-install-doc.html">produce formatted documentation, etc.</a>. -Fortunately, the file (<i>patch.doc</i>) may be input directly, and -“documentation” may found by reading the source of the package. -Roughly speaking, one gives the command a set of instructions -analogous to <i>sed</i> substitutions, and it regenerates the -command thus amended. Unless you can’t do your job any other way, -<i>patch</i> is best avoided. -<dl> -<dt><tt><i>etoolbox.sty</i></tt><dd><a href="http://mirror.ctan.org/macros/latex/contrib/etoolbox.zip">macros/latex/contrib/etoolbox</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/etoolbox/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/etoolbox.html">catalogue entry</a> -<dt><tt><i>patch.doc</i></tt><dd><a href="http://mirror.ctan.org/macros/generic/misc/patch.doc">macros/generic/misc/patch.doc</a>; <a href="http://mirror.ctan.org//help/Catalogue/entries/patch.html">catalogue entry</a> -<dt><tt><i>patchcommand.sty</i></tt><dd><a href="http://mirror.ctan.org/macros/latex/contrib/patchcmd.zip">macros/latex/contrib/patchcmd</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/patchcmd/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/patchcmd.html">catalogue entry</a> -<dt><tt><i>ted.sty</i></tt><dd><a href="http://mirror.ctan.org/macros/latex/contrib/ted.zip">macros/latex/contrib/ted</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/ted/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/ted.html">catalogue entry</a> -</dl> -<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=patch">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=patch</a> -</body> |