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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 |
<!DOCTYPE html>
<html lang="en">
<head>
<title>Conditional Macros - Glyph</title>
<link href='http://fonts.googleapis.com/css?family=Crimson+Text:400,400italic,600,600italic,700,700italic' rel='stylesheet' type='text/css'>
<meta charset="utf-8" />
<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="readability-verification" content="XmaVzRjmcFL5Bb2Fu9TZVdDKzhA3apQdxexTB2rK"/>
<meta name="description" content="H3RALD - Fabio Cevasco's Web Site" />
<meta name="keywords" content="h3rald, fabio cevasco, glyph" />
<link rel="shortcut icon" href="/favicon.png" type="image/png" />
<meta content="44.388041;9.073248" name="ICBM" />
<link rel="stylesheet" type="text/css" href="/styles/html5reset.css" />
<link rel="stylesheet" type="text/css" href="/styles/style.css" />
<script src="http://www.google.com/jsapi?key=ABQIAAAAr6RY1Z6dchG_sX9WDLSy3xRlq2n1sm52B5HDRR5tm6o8XM18FhR56xHNNH6CsX86uN5VoTrglpyOyQ" type="text/javascript"></script>
<script src="/js/sevenup.js" type="text/javascript"></script>
<script src="/js/sevenup_black.js" type="text/javascript"></script>
<script type="text/javascript">google.load("jquery", "1");</script>
<script src="/js/jquery-timeago.js" type="text/javascript"></script>
<script src="/js/jquery-easing.js" type="text/javascript"></script>
<script src="/js/jquery-fancybox.js" type="text/javascript"></script>
<script src="/js/date.js" type="text/javascript"></script>
<script src="/js/feeds.js" type="text/javascript"></script>
<script src="/js/hyphenator.js" type="text/javascript"></script>
<script src="/js/init.js" type="text/javascript"></script>
<script src="/js/search.js" type="text/javascript"></script>
</head>
<body>
<section id="container">
<header class="page">
<nav class="home-link">
<a href="/">
<img src="/images/h3rald_small.png" alt="H3RALD" class="default"/>
<![if !IE]>
<img src="/images/h3rald_hover_small.png" alt="H3RALD" class="hover"/>
<![endif]>
</a>
</nav>
<nav class="section">
/<a href="/glyph/" rel="glyph">GLYPH</a>
</nav>
</header>
<article class="page glyph-book">
<header>
<hgroup>
<h1>Conditional Macros</h1>
<h2>Glyph</h2>
</hgroup>
</header>
<section id="body-text" class="hyphenate glyph-book">
<nav class="navigation"><a href="/glyph/book/text_editing/inclusions.html">Content Reuse</a> | <a href="/glyph/book/index.html">Contents</a> | <a href="/glyph/book/text_editing/evaluation.html">Simple Programming and Code Evaluation</a></nav>
<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>
</ul>
<p>Consider the following code:</p>
<div class="CodeRay">
<div class="code"><pre><span class="line-numbers"><a href="#n1" name="n1">1</a></span>?[$[document.draft]|
<span class="line-numbers"><a href="#n2" name="n2">2</a></span>This is a first draft of the Glyph Book|
<span class="line-numbers"><a href="#n3" name="n3">3</a></span>This is the official version of the Glyph Book]
</pre></div>
</div>
<p>In this case, if <code>document.draft</code> is set to <code>true</code>, “This is a first draft of the Glyph Book” will be displayed; if not, “This is the official version of the Glyph Book” will be displayed instead.</p>
<p>The <a href="/glyph/book/macros/macros_core.html#m_condition"><code>condition</code></a> macro takes up to three parameters:</p>
<ol>
<li>the condition to evaluate</li>
<li>the text to include in the document only if the condition is satisfied.</li>
<li><em>(Optional)</em> the text to include in the document if the condition is <em>not</em> satisfied.</li>
</ol>
<p>Note that <em>all</em> parameters can contain macros, of course, so you can write things like:</p>
<div class="CodeRay">
<div class="code"><pre><span class="line-numbers"><a href="#n1" name="n1">1</a></span>?[and[
<span class="line-numbers"><a href="#n2" name="n2">2</a></span> eq[$[document.output]|pdf]
<span class="line-numbers"><a href="#n3" name="n3">3</a></span> |
<span class="line-numbers"><a href="#n4" name="n4">4</a></span> eq[$[tools.pdf_generator]|prince]
<span class="line-numbers"><a href="#n5" name="n5">5</a></span> ]
<span class="line-numbers"><a href="#n6" name="n6">6</a></span> |
<span class="line-numbers"><a href="#n7" name="n7">7</a></span> style[pagination.css]]
</pre></div>
</div>
<p>In this case, the <code>pagination.css</code> stylesheet is included only when you're generating a PDF document using Prince XML.</p>
<section class="section">
<header><h1 id="h_42">Results of conditional expressions</h1></header>
<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>
</section>
<nav class="navigation"><a href="/glyph/book/text_editing/inclusions.html">Content Reuse</a> | <a href="/glyph/book/index.html">Contents</a> | <a href="/glyph/book/text_editing/evaluation.html">Simple Programming and Code Evaluation</a></nav>
<nav id="sharing-buttons">
<a href="http://twitter.com/share" class="twitter-share-button" data-count="horizontal" data-via="h3rald">Tweet</a>
<script type="text/javascript" src="http://platform.twitter.com/widgets.js"></script>
<g:plusone size="medium"></g:plusone>
<script type="text/javascript">
(function() {
var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
po.src = 'https://apis.google.com/js/plusone.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
})();
</script>
</nav>
</section>
</article>
<footer>
<section class="ads">
<script type="text/javascript"><!--
google_ad_client = "pub-2871497824158668";
/* 728x90, created 9/10/10 */
google_ad_slot = "3963343166";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
</section>
<section>
<nav>
<a href="/about/">ABOUT</a>|<a href="/contact/">CONTACT</a>
</nav>
<p>H3RALD Web Site v8.1.2 © 2004 — 2011 <em>Fabio Cevasco</em></p>
</section>
</footer>
</section><!-- #container end -->
<!-- Start Google Analytics -->
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-18587377-1']);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>
<!-- End Google Analytics -->
<!-- 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 -->
</body>
</html>
|