content/glyph/book/text_editing/conditionals.html
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 |
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <title>Glyph</title> <meta name="author" content="Fabio Cevasco" /> <meta name="copyright" content="Fabio Cevasco" /> <meta name="generator" content="Glyph v0.4.0 (http://www.h3rald.com/glyph)" /> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <title>Conditional Macros - Glyph</title> <meta name="author" content="Fabio Cevasco" /> <meta name="copyright" content="Fabio Cevasco" /> <meta name="robots" content="all, follow" /> <meta name="Revisit-After" content="2 Days" /> <meta name="language" content="en" /> <meta name="target_country" content="en-us" /> <meta name="country" content="United States" /> <meta name="description" content="H3RALD - Fabio Cevasco's Web Site" /> <meta name="keywords" content="h3rald, fabio cevasco, glyph, technical writing, html, html5, book" /> <link rel="shortcut icon" href="/favicon.ico" type="image/x-icon" /> <meta http-equiv="content-type" content="text/html; charset=UTF-8" /> <meta content="44.388041;9.073248" name="ICBM" /> <link href="/css/main.css" media="all" rel="stylesheet" type="text/css" /> <link href="/glyph/book/styles/default.css" rel="stylesheet" type="text/css" /> </head> <body> <div id="wrapper"> <a href="http://github.com/h3rald/h3rald"><img style="position: absolute; top: 0; right: 0; border: 0;" src="http://s3.amazonaws.com/github/ribbons/forkme_right_red_aa0000.png" alt="Fork me on GitHub" /></a> <div id="header"> <!--[if lte IE 6]> <div id="ie-warning"> This site is not compatible with Internet Explorer 6 or lower. You should consider using a more modern browser for a better – and <em>safer</em> – web experience. [<a href="http://browsehappy.com/browsers/">Read More...</a>] </div> <![endif]--> <!-- HEADER START --> <div id="header-container"> <div id="header-left"> <h1><span class="logo"></span><a id="logo" href="/" title="H3RALD"></a></h1> </div> <div id="header-right"> <ul id="navigation"> <li><span class="preload nav-archives"></span><a id="nav-archives" href="/archives/" title="ARCHIVES"></a></li> <li><span class="preload nav-projects"></span><a id="nav-projects" href="/projects/" title="PROJECTS"></a></li> <li><span class="preload nav-about"></span><a id="nav-about" href="/about/" title="ABOUT"></a></li> <li><span class="preload nav-other"></span><a id="nav-other" href="/other/" title="OTHER"></a></li> </ul> </div> </div> </div> <!-- HEADER END --> <div class="ribbon"> </div> <!-- MAIN START --> <div id="main"> <!-- CONTAINER START --> <div id="container"> <!-- CONTENT START --> <div id="content" class="clearfixstandard"> <div id="page-links"> <span><script type="text/javascript" src="http://w.sharethis.com/button/sharethis.js#publisher=6e34d60c-b14e-4c19-9b2f-7c35a9f0ab09&type=website&linkfg=%23a4282d"></script></span> </div> <h2>Conditional Macros</h2> <hr /> <div id="content-body"> <div class="navigation"><a href="/glyph/book/text_editing/evaluation.html">Evaluating Ruby code and Configuration Settings ←</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/compiling/compiling.html">→ Compiling a project</a></div> <p>Sometimes you may want text to be included in a document only if certain conditions are satisfied. For example, you may want to display a disclaimer section only if the document is a draft (see the <a href="/glyph/book/config/document.html#s_document_draft"><code>document.draft</code></a> setting), or use a particular stylesheet only if when you generate a <span class="caps">PDF</span> document.</p> <p>To do so, you can use the <a href="/glyph/book/macros/macros_core.html#m_condition"><code>condition</code></a> macro (aliased by <code>?</code>), and a set of additional macros that can be used as conditional operators i.e.:</p> <ul> <li><a href="/glyph/book/macros/macros_core.html#m_eq"><code>eq</code></a> macro</li> <li><a href="/glyph/book/macros/macros_core.html#m_not"><code>not</code></a> macro</li> <li><a href="/glyph/book/macros/macros_core.html#m_and"><code>and</code></a> macro</li> <li><a href="/glyph/book/macros/macros_core.html#m_or"><code>or</code></a> macro</li> <li><a href="/glyph/book/macros/macros_core.html#m_match"><code>match</code></a> macro</li> </ul> <p>Consider the following code:</p> <pre class="lazy"><span class="line-numbers"> 1 </span> ?[$[document.draft]| <span class="line-numbers"> 2 </span> This is a first draft of the Glyph Book] <span class="line-numbers"> 3 </span> ?[not[$[document.draft]]| <span class="line-numbers"> 4 </span> This is the official version of the Glyph Book] </pre> <p>In this case, if <code>document.draft</code> is set to <code>true</code>, “This is a first draft of the Glyph Book” will be displayed; if not, “This is the official version of the Glyph Book” will be displayed instead.</p> <p>The <a href="/glyph/book/macros/macros_core.html#m_condition"><code>condition</code></a> macro takes two parameters:</p> <ul> <li>the first one is the condition to evaluate</li> <li>the second one is the text to include in the document only if the condition is satisfied.</li> </ul> <p>Note that <em>both</em> parameters can contain macros, of course, so you can write things like:</p> <pre class="lazy"><span class="line-numbers"> 1 </span> ?[and[ <span class="line-numbers"> 2 </span> eq[$[document.output]|pdf] <span class="line-numbers"> 3 </span> | <span class="line-numbers"> 4 </span> eq[$[tools.pdf_generator]|prince] <span class="line-numbers"> 5 </span> ] <span class="line-numbers"> 6 </span> | <span class="line-numbers"> 7 </span> style[pagination.css]] </pre> <p>In this case, the <code>pagination.css</code> stylesheet is included only when you're generating a PDF document using Prince XML.</p> <div class="section"> <h4 id="h_38">Results of conditional expressions</h4> <p>The <a href="/glyph/book/macros/macros_core.html#m_condition"><code>condition</code></a> macro in Glyph works in a similar way as conditionals in programming languages: if the conditional expression (supplied as first parameter) is satisfied then the second parameter is executed or displayed. But when is a conditional expression satisfied? Glyph is a simple mini-language to perform text manipulation, and has no types, it can only understand text, therefore:</p> <ul> <li>A conditional expression is satisfied if it evaluates to a non-empty string except “false”.</li> <li>A conditional expression is not satisfied if it evaluates to an empty string or the string “false”.</li> </ul> </div> <div class="navigation"><a href="/glyph/book/text_editing/evaluation.html">Evaluating Ruby code and Configuration Settings ←</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/compiling/compiling.html">→ Compiling a project</a></div> </div> <div id="content-footer"> <div class="share"> <script type="text/javascript"><!-- google_ad_client = "pub-2871497824158668"; /* 728x90, h3rald 8.0 */ google_ad_slot = "0081634732"; google_ad_width = 728; google_ad_height = 90; //--> </script> <script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script> </div> </div> </div> <!-- CONTENT END --> </div> <!-- CONTAINER END --> </div> <div class="ribbon"></div> <!-- MAIN END --> <div id="border-bottom"> <div id="services"> <div class ="footer-left"> <div id="backtype"> <h3><span class="s-opinions preload"></span><a id="s-opinions" href="http://www.backtype.com/h3rald" title="Opinions"></a></h3> </div> </div> <div class ="footer-center"> <div id="twitter"> <h3><span class="s-tweets preload"></span><a id="s-tweets" href="http://www.twitter.com/h3rald" title="Tweets"></a></h3> </div> </div> <div class ="footer-right"> <div id="delicious"> <h3><span class="s-bookmarks preload"></span><a id="s-bookmarks" href="http://www.delicious.com/h3rald" title="Bookmarks"></a></h3> </div> </div> </div> <!-- SERVICES END --> </div> <div class="clearfooter"></div> </div> <!-- WRAPPER END --> <div id="footer"> <div id="footer-container"> <div class="footer-div"> H3RALD Web Site v8.0.0 <em>"xStatic"</em> — © 2004-2010 <strong>Fabio Cevasco</strong> — <a class="link" href="http://creativecommons.org/licenses/by-nc-nd/3.0/us/">Some rights reserved</a> | <a href="http://validator.w3.org/check?uri=referer" class="link">XHTML 1.1</a> | <a href="http://jigsaw.w3.org/css-validator/validator?uri=/cond_macros.html" class="link">CSS 2.1</a> </div> </div> <!-- END FOOTER CONTAINER--> </div> <!-- END FOOTER --> <!-- Start of StatCounter Code --> <script type="text/javascript"> var sc_project=6193656; var sc_invisible=1; var sc_security="57f7ee2a"; </script> <script type="text/javascript" src="http://www.statcounter.com/counter/counter_xhtml.js"></script> <!-- End of StatCounter Code --> <script src='http://www.google-analytics.com/ga.js' type='text/javascript'></script> <script src="http://www.google.com/jsapi?key=ABQIAAAA6h3j8Jri5D_da53UPbEbThRlq2n1sm52B5HDRR5tm6o8XM18FhTKn3v155RpPeD0kWnWG81QEhhifQ" type="text/javascript"></script> <script src="/js/compressed.js" type="text/javascript"></script> </body> </html> |