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diff --git a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-whatengine.html b/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-whatengine.html deleted file mode 100644 index 47d47effccd..00000000000 --- a/Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-whatengine.html +++ /dev/null @@ -1,108 +0,0 @@ -<head> -<title>UK TeX FAQ -- question label whatengine</title> -</head><body> -<h3>Am I using PDFTeX, XeTeX or LuaTeX?</h3> -<p/><p/>You often need to know what “engine” your macros are running on (the -engine is the TeX-derivative or TeX-alike processor that -typesets your document). The reason that you need to know is that the -set of functions available in each engine is different. Thus, for -TeX macros to run on any engine, they need to “know” what they -can and cannot do, which depends on the engine in use. Getting the -right answer is surprisingly tricky (see below for an elaboration of -one apparently simple test). -<p/>There is now a comprehensive set of packages that answer the question -for you. They all create a TeX conditional command: -<ul> -<li> <i>ifpdf</i> creates a command <code>\</code><code>ifpdf</code>, -<li> <i>ifxetex</i> creates a command <code>\</code><code>ifxetex</code> and -<li> <i>ifluatex</i> creates a command <code>\</code><code>ifluatex</code>. -</ul> -These TeX commands may be used within the LaTeX conditional -framework, as (for example): -<blockquote> - <code>\</code><code>ifthenelse</code><code>\char‘{</code><code>\</code><code>boolean{pdf}</code><code>\char‘}\char‘{<<i>if pdf</i>>\char‘}\char‘{<<i>not pdf</i>>\char‘}</code> -</blockquote><p> -<p/>The <i>ifxetex</i> package also provides a command -<code>\</code><code>RequireXeTeX</code> which creates an error if the code is not running -under XeTeX; while the other packages don’t provide such a command, -it’s not really difficult to write one for yourself. -<p/> - -<p/>Now for those who want to do the job for themselves: here’s a -discussion of doing the job for PDFTeX and <code>\</code><code>ifpdf</code> — the -eager programmer can regenerate <code>\</code><code>ifxetex</code> or <code>\</code><code>ifluatex</code> in the -same fashion. It’s not recommended\dots -<p/>Suppose you need to test whether your output will be PDF or -DVI. The natural thing is to check whether you have access to -some PDFTeX-only primitive; a good one to try (not least because it -was present in the very first releases of PDFTeX) is -<code>\</code><code>pdfoutput</code>. So you try -<blockquote> -<pre> -\ifx\pdfoutput\undefined - ... % not running PDFTeX -\else - ... % running PDFTeX -\fi -</pre> -</blockquote><p> -Except that neither branch of this conditional is rock-solid. The -first branch can be misleading, since the “awkward” user could have -written: -<blockquote> -<pre> -\let\pdfoutput\undefined -</pre> -</blockquote><p> -so that your test will falsely choose the first alternative. While -this is a theoretical problem, it is unlikely to be a major one. -<p/>More important is the user who loads a package that uses -LaTeX-style testing for the command name’s existence (for example, -the LaTeX <i>graphics</i> package, which is useful even to the -Plain TeX user). Such a package may have gone ahead of you, so the -test may need to be elaborated: -<blockquote> -<pre> -\ifx\pdfoutput\undefined - ... % not running PDFTeX -\else - \ifx\pdfoutput\relax - ... % not running PDFTeX - \else - ... % running PDFTeX - \fi -\fi -</pre> -</blockquote><p> -If you only want to know whether some PDFTeX extension (such as -marginal kerning) is present, you can stop at this point: you know as -much as you need. -<p/>However, if you need to know whether you’re creating PDF -output, you also need to know about the value of <code>\</code><code>pdfoutput</code>: -<blockquote> -<pre> -\ifx\pdfoutput\undefined - ... % not running PDFTeX -\else - \ifx\pdfoutput\relax - ... % not running PDFTeX - \else - % running PDFTeX, with... - \ifnum\pdfoutput>0 - ... % PDF output - \else - ... % DVI output - \fi - \fi -\fi -</pre> -</blockquote><p> -<dl> -<dt><tt><i>ifpdf.sty</i></tt><dd>Distributed as part Heiko Oberdiek’s bundle - <a href="http://mirror.ctan.org/macros/latex/contrib/oberdiek.zip">macros/latex/contrib/oberdiek</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/oberdiek/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/ifpdf.html">catalogue entry</a> -<dt><tt><i>ifluatex.sty</i></tt><dd>Distributed as part of Heiko Oberdiek’s bundle - <a href="http://mirror.ctan.org/macros/latex/contrib/oberdiek.zip">macros/latex/contrib/oberdiek</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/oberdiek/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/ifluatex.html">catalogue entry</a> -<dt><tt><i>ifxetex.sty</i></tt><dd><a href="http://mirror.ctan.org/macros/generic/ifxetex.zip">macros/generic/ifxetex</a> (or <a href="http://mirror.ctan.org/macros/generic/ifxetex/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/ifxetex.html">catalogue entry</a> -</dl> -<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=whatengine">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=whatengine</a> -</body> |