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diff --git a/doc/groff.html.node/Requests-and-Macros.html b/doc/groff.html.node/Requests-and-Macros.html new file mode 100644 index 0000000..8a009b3 --- /dev/null +++ b/doc/groff.html.node/Requests-and-Macros.html @@ -0,0 +1,221 @@ +<!DOCTYPE html> +<html> +<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ --> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<!-- This manual documents GNU troff version 1.23.0. + +Copyright © 1994-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A +copy of the license is included in the section entitled "GNU Free +Documentation License". --> +<title>Requests and Macros (The GNU Troff Manual)</title> + +<meta name="description" content="Requests and Macros (The GNU Troff Manual)"> +<meta name="keywords" content="Requests and Macros (The GNU Troff Manual)"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta name="viewport" content="width=device-width,initial-scale=1"> + +<link href="index.html" rel="start" title="Top"> +<link href="Request-Index.html" rel="index" title="Request Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Text.html" rel="up" title="Text"> +<link href="Macro-Packages.html" rel="next" title="Macro Packages"> +<link href="Tabs-and-Leaders.html" rel="prev" title="Tabs and Leaders"> +<style type="text/css"> +<!-- +div.example {margin-left: 3.2em} +--> +</style> + + +</head> + +<body lang="en"> +<div class="subsection-level-extent" id="Requests-and-Macros"> +<div class="nav-panel"> +<p> +Next: <a href="Macro-Packages.html" accesskey="n" rel="next">Macro Packages</a>, Previous: <a href="Tabs-and-Leaders.html" accesskey="p" rel="prev">Tabs and Leaders</a>, Up: <a href="Text.html" accesskey="u" rel="up">Text</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<h4 class="subsection" id="Requests-and-Macros-1">5.1.7 Requests and Macros</h4> + +<p>We have now encountered almost all of the syntax there is in the +<code class="code">roff</code> language, with an exception already noted in passing. +<a class="index-entry-id" id="index-request"></a> +<a class="index-entry-id" id="index-control-character-_0028_002e_0029"></a> +<a class="index-entry-id" id="index-character_002c-control-_0028_002e_0029"></a> +<a class="index-entry-id" id="index-no_002dbreak-control-character-_0028_0027_0029"></a> +<a class="index-entry-id" id="index-character_002c-no_002dbreak-control-_0028_0027_0029"></a> +<a class="index-entry-id" id="index-control-character_002c-no_002dbreak-_0028_0027_0029"></a> +A <em class="dfn">request</em> is an instruction to the formatter that occurs after a +<em class="dfn">control character</em>, which is recognized at the beginning of an +input line. The regular control character is a dot (<code class="code">.</code>). Its +counterpart, the <em class="dfn">no-break control character</em>, a neutral apostrophe +(<code class="code">'</code>), suppresses the break that is implied by some requests. +These characters were chosen because it is uncommon for lines of text in +natural languages to begin with them. +<a class="index-entry-id" id="index-dummy-character-_0028_005c_0026_0029_002c-as-control-character-suppressor"></a> +<a class="index-entry-id" id="index-character_002c-dummy-_0028_005c_0026_0029_002c-as-control-character-suppressor"></a> +If you require a formatted period or apostrophe (closing single +quotation mark) where GNU <code class="code">troff</code> is expecting a control character, +prefix the dot or neutral apostrophe with the dummy character escape +sequence, ‘<samp class="samp">\&</samp>’. +</p> +<a class="index-entry-id" id="index-control-line"></a> +<p>An input line beginning with a control character is called a +<em class="dfn">control line</em>. +<a class="index-entry-id" id="index-text-line"></a> +Every line of input that is not a control line is a <em class="dfn">text +line</em>.<a class="footnote" id="DOCF25" href="groff.html_fot.html#FOOT25"><sup>25</sup></a> +</p> +<a class="index-entry-id" id="index-argument"></a> +<p>Requests often take <em class="dfn">arguments</em>, words (separated from the request +name and each other by spaces) that specify details of the action GNU +<code class="code">troff</code> is expected to perform. If a request is meaningless +without arguments, it is typically ignored. +</p> +<p>GNU <code class="code">troff</code>’s requests and escape sequences comprise the control +language of the formatter. Of key importance are the requests that +define macros. Macros are invoked like requests, enabling the request +repertoire to be extended or overridden.<a class="footnote" id="DOCF26" href="groff.html_fot.html#FOOT26"><sup>26</sup></a> +</p> +<a class="index-entry-id" id="index-macro"></a> +<a class="index-entry-id" id="index-calling-a-macro"></a> +<a class="index-entry-id" id="index-interpolation"></a> +<p>A <em class="dfn">macro</em> can be thought of as an abbreviation you can define for a +collection of control and text lines. When the macro is <em class="dfn">called</em> by +giving its name after a control character, it is replaced with what it +stands for. The process of textual replacement is known as +<em class="dfn">interpolation</em>.<a class="footnote" id="DOCF27" href="groff.html_fot.html#FOOT27"><sup>27</sup></a> Interpolations are handled as soon as they are +recognized, and once performed, a <code class="code">roff</code> formatter scans the +replacement for further requests, macro calls, and escape sequences. +</p> +<p>In <code class="code">roff</code> systems, the <code class="code">de</code> request defines a +macro.<a class="footnote" id="DOCF28" href="groff.html_fot.html#FOOT28"><sup>28</sup></a> +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de DATE +2020-11-14 +.. +</pre></div></div> + +<p>The foregoing input produces no output by itself; all we have done is +store some information. Observe the pair of dots that ends the macro +definition. This is a default; you can specify your own terminator for +the macro definition as the second argument to the <code class="code">de</code> request. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de NAME ENDNAME +Heywood Jabuzzoff +.ENDNAME +</pre></div></div> + +<p>In fact, the ending marker is itself the name of a macro to be +called, or a request to be invoked, if it is defined at the time its +control line is read. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de END +Big Rip +.. +.de START END +Big Bang +.END +.START + ⇒ Big Rip Big Bang +</pre></div></div> + +<p>In the foregoing example, “Big Rip” printed before “Big Bang” +because its macro was <em class="emph">called</em> first. Consider what would happen +if we dropped <code class="code">END</code> from the ‘<samp class="samp">.de START</samp>’ line and added +<code class="code">..</code> after <code class="code">.END</code>. Would the order change? +</p> +<p>Let us consider a more elaborate example. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de DATE +2020-10-05 +.. +. +.de BOSS +D.\& Kruger, +J.\& Peterman +.. +. +.de NOTICE +Approved: +.DATE +by +.BOSS +.. +. +Insert tedious regulatory compliance paragraph here. + +.NOTICE + +Insert tedious liability disclaimer paragraph here. + +.NOTICE + ⇒ Insert tedious regulatory compliance paragraph here. + ⇒ + ⇒ Approved: 2020-10-05 by D. Kruger, J. Peterman + ⇒ + ⇒ Insert tedious liability disclaimer paragraph here. + ⇒ + ⇒ Approved: 2020-10-05 by D. Kruger, J. Peterman +</pre></div></div> + +<p>The above document started with a series of control lines. Three macros +were defined, with a <code class="code">de</code> request declaring each macro’s name, and +the “body” of the macro starting on the next line and continuing until +a line with two dots ‘<samp class="samp"><code class="code">..</code></samp>’ marked its end. The text proper +began only after the macros were defined; this is a common pattern. +Only the <code class="code">NOTICE</code> macro was called “directly” by the document; +<code class="code">DATE</code> and <code class="code">BOSS</code> were called only by <code class="code">NOTICE</code> itself. +Escape sequences were used in <code class="code">BOSS</code>, two levels of macro +interpolation deep. +</p> +<p>The advantage in typing and maintenance economy may not be obvious from +such a short example, but imagine a much longer document with dozens of +such paragraphs, each requiring a notice of managerial approval. +Consider what must happen if you are in charge of generating a new +version of such a document with a different date, for a different boss. +With well-chosen macros, you only have to change each datum in one +place. +</p> +<p>In practice, we would probably use strings (see <a class="pxref" href="Strings.html">Strings</a>) instead of +macros for such simple interpolations; what is important here is to +glimpse the potential of macros and the power of recursive +interpolation. +</p> +<p>We could have defined <code class="code">DATE</code> and <code class="code">BOSS</code> in the opposite order; +perhaps less obviously, we could also have defined them <em class="emph">after</em> +<code class="code">NOTICE</code>. “Forward references” like this are acceptable because +the body of a macro definition is not (completely) interpreted, but +stored instead (see <a class="pxref" href="Copy-Mode.html">Copy Mode</a>). While a macro is being defined (or +appended to), requests are not interpreted and macros not interpolated, +whereas some commonly used escape sequences <em class="emph">are</em> interpreted. +<code class="code">roff</code> systems also support recursive macro calls, as long as you +have a way to break the recursion (see <a class="pxref" href="Conditionals-and-Loops.html">Conditionals and Loops</a>). +Maintainable <code class="code">roff</code> documents tend to arrange macro definitions to +minimize forward references. +</p> + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Macro-Packages.html">Macro Packages</a>, Previous: <a href="Tabs-and-Leaders.html">Tabs and Leaders</a>, Up: <a href="Text.html">Text</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |