all repos — h3rald @ 584dc768555a890c50ae175d619f8e660987cb70

The sources of https://h3rald.com

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
 
<!DOCTYPE html> 
<html lang="en"> 
	<head> 
		<title>Glyph - Conditional Macros</title> 



		<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="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" /> 

		<!--[if lte IE 8]>
		<script src="/js/html5.js" type="text/javascript"></script>
		<![endif]--> 
	</head> 
	<body> 
		<!--[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 &ndash; and <em>safer</em> &ndash; web experience. [<a href="http://browsehappy.com/browsers/">Read More &raquo;</a>]
		</div>
		<![endif]--> 

		<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="/projects/" rel="archives">PROJECTS</a> 
				</nav> 

			</header> 
			<article class="page"> 
				<header> 
					<hgroup> 
					<h1>Conditional Macros</h1> 
					</hgroup> 
				</header> 
				<section id="body-text" class="hyphenate"> 

							<nav><a href="/glyph/book/text_editing/evaluation.html">Evaluating Ruby code and Configuration Settings &larr;</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/compiling/compiling.html">&rarr; Compiling a project</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>
	<li><a href="/glyph/book/macros/macros_core.html#m_match"><code>match</code></a> macro</li>
</ul>
<p>Consider the following code:</p>
	<div class="CodeRay">
  <div class="code"><pre><span class="no">1</span> ?[$[document.draft]|
<span class="no">2</span> This is a first draft of the Glyph Book]
<span class="no">3</span> ?[not[$[document.draft]]|
<span class="no">4</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>, &#8220;This is a first draft of the Glyph Book&#8221; will be displayed; if not, &#8220;This is the official version of the Glyph Book&#8221; 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>
	<div class="CodeRay">
  <div class="code"><pre><span class="no">1</span> ?[and[
<span class="no">2</span>     eq[$[document.output]|pdf]
<span class="no">3</span>     |
<span class="no">4</span>     eq[$[tools.pdf_generator]|prince]
<span class="no">5</span>     ]
<span class="no">6</span>   |
<span class="no">7</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_38">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 &#8220;false&#8221;.</li>
	<li>A conditional expression is not satisfied if it evaluates to an empty string or the string &#8220;false&#8221;.</li>
</ul>

</section>
							<nav><a href="/glyph/book/text_editing/evaluation.html">Evaluating Ruby code and Configuration Settings &larr;</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/compiling/compiling.html">&rarr; Compiling a project</a></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 &mdash; &copy; 2010 &mdash; <em>Fabio Cevasco</em></p> 
				</section> 
			</footer> 
		</section><!-- #container end --> 
		<script src="http://www.google.com/jsapi?key=ABQIAAAAr6RY1Z6dchG_sX9WDLSy3xRlq2n1sm52B5HDRR5tm6o8XM18FhR56xHNNH6CsX86uN5VoTrglpyOyQ" type="text/javascript"></script> 
		<!-- <script src="/js/jquery.js" type="text/javascript"></script> --> 
		<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></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/jquery-toc.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/search.js" type="text/javascript"></script> 
		<script src="/js/hyphenator.min.js" type="text/javascript"></script> 
		<script src="/js/init.js" type="text/javascript"></script> 
		<!-- 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>