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diff --git a/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-empty.html b/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-empty.html new file mode 100644 index 00000000000..170867a7716 --- /dev/null +++ b/Master/texmf-doc/doc/english/FAQ-en/html/FAQ-empty.html @@ -0,0 +1,36 @@ +<head> +<title>UK TeX FAQ -- question label empty</title> +</head><body> +<h3>Detecting that something is empty</h3> +<p>Suppose you need to know that the argument of your command is empty: +that is, to distinguish between <code>\</code><code>cmd{}</code> +and <code>\</code><code>cmd{blah}</code>. This is pretty simple: +<blockquote> +<pre> +\def\cmd#1{% + \def\tempa{}% + \def\tempb{#1}% + \ifx\tempa\tempb + <empty case> + \else + <non-empty case> + \fi +} +</pre> +</blockquote> +The case where you want to ignore an argument that consists of nothing +but spaces, rather than something completely empty, is more tricky. +It's solved in the code fragment <i>ifmtarg</i>, which defines +commands <code>\</code><code>@ifmtarg</code> and <code>\</code><code>@ifnotmtarg</code>, which distinguish (in +opposite directions) between a second and third argument. The +package's code also appears in the LaTeX <i>memoir</i> class. +<p><i>Ifmtarg</i> makes challenging reading; there's also a discussion of the +issue in number two of the "around the bend" articles by the late +lamented Mike Downes. +<dl> +<dt><tt><i>Around the bend series</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/info/aro-bend.zip">info/aro-bend</a> (<a href="ftp://cam.ctan.org/tex-archive/info/aro-bend.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/info/aro-bend/">browse</a>) +<dt><tt><i>ifmtarg.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/misc/ifmtarg.sty">macros/latex/contrib/misc/ifmtarg.sty</a> +<dt><tt><i>memoir.cls</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/memoir.zip">macros/latex/contrib/memoir</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/memoir.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/memoir/">browse</a>) +</dl> +<p><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=empty">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=empty</a> +</body> |