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diff --git a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-cvtlatex.html b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-cvtlatex.html deleted file mode 100644 index 66c40d9b7ed..00000000000 --- a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-cvtlatex.html +++ /dev/null @@ -1,77 +0,0 @@ -<head> -<title>UK TeX FAQ -- question label cvtlatex</title> -</head><body> -<h3>Transcribing LaTeX command definitions</h3> -<p/>At several places in this FAQ, questions are answered in terms -of how to program a LaTeX macro. Sometimes, these macros might -also help users of Plain TeX or other packages; this answer -attempts to provide a rough-and-ready guide to transcribing such macro -definitions for use in other packages. -<p/>The reason LaTeX has commands that replace <code>\</code><code>def</code>, is that -there’s a general philosophy within LaTeX that the user should be -protected from himself: the user has different commands according to -whether the command to be defined exists (<code>\</code><code>renewcommand</code>) or not -(<code>\</code><code>newcommand</code>), and if its status proves not as the user expected, -an error is reported. A third definition command, -<code>\</code><code>providecommand</code>, only defines if the target is not already -defined; LaTeX has no direct equivalent of <code>\</code><code>def</code>, which ignores -the present state of the command. The final command of this sort is -<code>\</code><code>DeclareRobustCommand</code>, which creates a command which is “robust” -(i.e., will not expand if subjected to LaTeX “protected -expansion”); from the Plain TeX user’s point of view, -<code>\</code><code>DeclareRobustCommand</code> should be treated as a non-checking version -of <code>\</code><code>newcommand</code>. -<p/>LaTeX commands are, by default, defined <code>\</code><code>long</code>; an optional <code>*</code> -between the <code>\</code><code>newcommand</code> and its (other) arguments specifies that -the command is <em>not</em> to be defined <code>\</code><code>long</code>. The <code>*</code> is -detected by a command <code>\</code><code>@ifstar</code> which uses <code>\</code><code>futurelet</code> to switch -between two branches, and gobbles the <code>*</code>: LaTeX users are -encouraged to think of the <code>*</code> as part of the command name. -<p/>LaTeX’s checks for unknown command are done by <code>\</code><code>ifx</code> comparison -of a <code>\</code><code>csname</code> construction with <code>\</code><code>relax</code>; since the command name -argument is the desired control sequence name, this proves a little -long-winded. Since <code>#1</code> is the requisite argument, we have: -<blockquote> - -<pre> -\expandafter\ifx - \csname\expandafter\@gobble\string#1\endcsname - \relax - ... -</pre> -</blockquote><p> -(<code>\</code><code>@gobble</code> simply throws away its argument). -<p/>The arguments of a LaTeX command are specified by two optional -arguments to the defining command: a count of arguments (0–9: if the -count is 0, the optional count argument may be omitted), and a default -value for the first argument, if the defined command’s first argument -is to be optional. So: -<blockquote> -<pre> -\newcommand\foo{...} -\newcommand\foo[0]{...} -\newcommand\foo[1]{...#1...} -\newcommand\foo[2][boo]{...#1...#2...} -</pre> -</blockquote><p> -In the last case, <code>\</code><code>foo</code> may be called as <code>\</code><code>foo{goodbye}</code>, -which is equivalent to <code>\</code><code>foo[boo]{goodbye}</code> (employing the -default value given for the first argument), or as -<code>\</code><code>foo[hello]{goodbye}</code> (with an explicit first argument). -<p/>Coding of commands with optional arguments is exemplified by the -coding of the last <code>\</code><code>foo</code> above: -<blockquote> -<pre> -\def\foo{\futurelet\next\@r@foo} -\def\@r@foo{\ifx\next[% - \let\next\@x@foo - \else - \def\next{\@x@foo[boo]}% - \fi - \next -} -\def\@x@foo[#1]#2{...#1...#2...} -</pre> -</blockquote><p> -<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=cvtlatex">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=cvtlatex</a> -</body> |