diff options
Diffstat (limited to '')
| -rw-r--r-- | doc/groff.html.node/Writing-Macros.html | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/doc/groff.html.node/Writing-Macros.html b/doc/groff.html.node/Writing-Macros.html new file mode 100644 index 0000000..e08b9fa --- /dev/null +++ b/doc/groff.html.node/Writing-Macros.html @@ -0,0 +1,267 @@ +<!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>Writing Macros (The GNU Troff Manual)</title> + +<meta name="description" content="Writing Macros (The GNU Troff Manual)"> +<meta name="keywords" content="Writing 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="GNU-troff-Reference.html" rel="up" title="GNU troff Reference"> +<link href="Page-Motions.html" rel="next" title="Page Motions"> +<link href="Conditionals-and-Loops.html" rel="prev" title="Conditionals and Loops"> +<style type="text/css"> +<!-- +a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} +div.example {margin-left: 3.2em} +span.r {font-family: initial; font-weight: normal; font-style: normal} +span:hover a.copiable-link {visibility: visible} +strong.def-name {font-family: monospace; font-weight: bold; font-size: larger} +--> +</style> + + +</head> + +<body lang="en"> +<div class="section-level-extent" id="Writing-Macros"> +<div class="nav-panel"> +<p> +Next: <a href="Page-Motions.html" accesskey="n" rel="next">Page Motions</a>, Previous: <a href="Conditionals-and-Loops.html" accesskey="p" rel="prev">Conditionals and Loops</a>, Up: <a href="GNU-troff-Reference.html" accesskey="u" rel="up">GNU <code class="code">troff</code> Reference</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> +<h3 class="section" id="Writing-Macros-1">5.24 Writing Macros</h3> +<a class="index-entry-id" id="index-writing-macros"></a> +<a class="index-entry-id" id="index-macros_002c-writing"></a> + +<p>A <em class="dfn">macro</em> is a stored collection of text and control lines that can +be interpolated multiple times. Use macros to define common operations. +Macros are called in the same way that requests are invoked. While +requests exist for the purpose of creating macros, simply calling an +undefined macro, or interpolating it as a string, will cause it to be +defined as empty. See <a class="xref" href="Identifiers.html">Identifiers</a>. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ede"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.de</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002ede'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-de"></a> +<p>Define a macro <var class="var">name</var>, replacing the definition of any existing +request, macro, string, or diversion called <var class="var">name</var>. If +<var class="var">name</var> already exists as an alias, the target of the alias is +redefined; recall <a class="ref" href="Strings.html">Strings</a>. GNU <code class="code">troff</code> enters copy +mode,<a class="footnote" id="DOCF97" href="groff.html_fot.html#FOOT97"><sup>97</sup></a> storing subsequent input lines as the +macro definition. If the optional second argument is not specified, the +definition ends with the control line ‘<samp class="samp">..</samp>’ (two dots). +Alternatively, <var class="var">end</var> identifies a macro whose call syntax at the +start of a control line ends the definition of <var class="var">name</var>; <var class="var">end</var> is +then called normally. A macro definition must end in the same +conditional block (if any) in which it began (see <a class="pxref" href="Conditional-Blocks.html">Conditional Blocks</a>). Spaces or tabs are permitted after the control character in +the line containing this ending token (either ‘<samp class="samp">.</samp>’ or +‘<samp class="samp"><var class="var">end</var></samp>’), but a tab immediately after the token prevents its +recognition as the end of a macro definition. The macro <var class="var">end</var> can +be called with arguments.<a class="footnote" id="DOCF98" href="groff.html_fot.html#FOOT98"><sup>98</sup></a> +</p> +<p>Here is a small example macro called ‘<samp class="samp">P</samp>’ that causes a break and +inserts some vertical space. It could be used to separate paragraphs. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de P +. br +. sp .8v +.. +</pre></div></div> + +<p>We can define one macro within another. Attempting to nest ‘<samp class="samp">..</samp>’ +naïvely will end the outer definition because the inner definition +isn’t interpreted as such until the outer macro is later interpolated. +We can use an end macro instead. Each level of nesting should use a +unique end macro. +</p> +<p>An end macro need not be defined until it is called. This fact enables +a nested macro definition to begin inside one macro and end inside +another. Consider the following example.<a class="footnote" id="DOCF99" href="groff.html_fot.html#FOOT99"><sup>99</sup></a> +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de m1 +. de m2 m3 +you +.. +.de m3 +Hello, +Joe. +.. +.de m4 +do +.. +.m1 +know? +. m3 +What +.m4 +.m2 + ⇒ Hello, Joe. What do you know? +</pre></div></div> + +<p>A nested macro definition <em class="emph">can</em> be terminated with ‘<samp class="samp">..</samp>’ and +nested macros <em class="emph">can</em> reuse end macros, but these control lines must +be escaped multiple times for each level of nesting. The necessity of +this escaping and the utility of nested macro definitions will become +clearer when we employ macro parameters and consider the behavior of +copy mode in detail. +</p></dd></dl> + +<p><code class="code">de</code> defines a macro that inherits the compatibility mode +enablement status of its context (see <a class="pxref" href="Implementation-Differences.html">Implementation Differences</a>). +Often it is desirable to make a macro that uses <code class="code">groff</code> features +callable from contexts where compatibility mode is on; for instance, +when writing extensions to a historical macro package. To achieve this, +compatibility mode needs to be switched off while such a macro is +interpreted—without disturbing that state when it is finished. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ede1"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.de1</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002ede1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-de1"></a> +<p>The <code class="code">de1</code> request defines a macro to be interpreted with +compatibility mode disabled. When <var class="var">name</var> is called, compatibility +mode enablement status is saved; it is restored when the call completes. +Observe the extra backlash before the interpolation of register +‘<samp class="samp">xxx</samp>’; we’ll explore this subject in <a class="ref" href="Copy-Mode.html">Copy Mode</a>. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr xxx 12345 +.de aa +The value of xxx is \\n[xxx]. +. br +.. +.de1 bb +The value of xxx is \\n[xxx]. +.. +.cp 1 +.aa + error→ warning: register '[' not defined + ⇒ The value of xxx is 0xxx]. +.bb + ⇒ The value of xxx is 12345. +</pre></div></div> +</dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002edei"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.dei</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002edei'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-dei"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002edei1"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.dei1</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002edei1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-dei1"></a> +<p>The <code class="code">dei</code> request defines a macro with its name and end +macro indirected through strings. That is, it interpolates strings +named <var class="var">name</var> and <var class="var">end</var> before performing the definition. +</p> +<p>The following examples are equivalent. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.ds xx aa +.ds yy bb +.dei xx yy +</pre></div></div> + +<div class="example"> +<div class="group"><pre class="example-preformatted">.de aa bb +</pre></div></div> + +<p>The <code class="code">dei1</code> request bears the same relationship to <code class="code">dei</code> as +<code class="code">de1</code> does to <code class="code">de</code>; it temporarily turns compatibility mode +off when <var class="var">name</var> is called. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002eam"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.am</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002eam'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-am"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eam1"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.am1</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002eam1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-am1"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eami"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.ami</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002eami'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-ami"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eami1"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.ami1</code></strong> <var class="def-var-arguments">name [<span class="r"><i class="slanted">end</i></span>]</var><a class="copiable-link" href='#index-_002eami1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-ami1"></a> +<a class="index-entry-id" id="index-appending-to-a-macro-_0028am_0029"></a> +<a class="index-entry-id" id="index-macro_002c-appending-to-_0028am_0029"></a> +<p><code class="code">am</code> appends subsequent input lines to macro <var class="var">name</var>, extending +its definition, and otherwise working as <code class="code">de</code> does. +</p> +<p>To make the previously defined ‘<samp class="samp">P</samp>’ macro set indented instead of +block paragraphs, add the necessary code to the existing macro. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.am P +.ti +5n +.. +</pre></div></div> + +<p>The other requests are analogous to their ‘<samp class="samp">de</samp>’ counterparts. The +<code class="code">am1</code> request turns off compatibility mode during interpretation of +the appendment. The <code class="code">ami</code> request appends indirectly, meaning that +strings <var class="var">name</var> and <var class="var">end</var> are interpolated with the resulting +names used before appending. The <code class="code">ami1</code> request is similar to +<code class="code">ami</code>, disabling compatibility mode during interpretation of the +appended lines. +</p></dd></dl> + +<a class="index-entry-id" id="index-trace_002etmac"></a> +<p>Using <samp class="file">trace.tmac</samp>, you can trace calls to <code class="code">de</code>, +<code class="code">de1</code>, <code class="code">am</code>, and <code class="code">am1</code>. You can also use the +<code class="code">backtrace</code> request at any point desired to troubleshoot tricky +spots (see <a class="pxref" href="Debugging.html">Debugging</a>). +</p> +<p>See <a class="xref" href="Strings.html">Strings</a>, for the <code class="code">als</code>, <code class="code">rm</code>, and <code class="code">rn</code> requests to +create an alias of, remove, and rename a macro, respectively. +</p> +<a class="index-entry-id" id="index-object-creation"></a> +<p>Macro identifiers share their name space with requests, strings, and +diversions; see <a class="ref" href="Identifiers.html">Identifiers</a>. The <code class="code">am</code>, <code class="code">as</code>, <code class="code">da</code>, +<code class="code">de</code>, <code class="code">di</code>, and <code class="code">ds</code> requests (together with their +variants) create a new object only if the name of the macro, diversion, +or string is currently undefined or if it is defined as a request; +normally, they modify the value of an existing object. See <a class="xref" href="Strings.html#als">the +description of the <code class="code">als</code> request</a>, for pitfalls when redefining a +macro that is aliased. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ereturn"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.return</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">anything</i></span>]</var><a class="copiable-link" href='#index-_002ereturn'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-return"></a> +<p>Exit a macro, immediately returning to the caller. If called with an +argument <var class="var">anything</var>, exit twice—the current macro and the macro +one level higher. This is used to define a wrapper macro for +<code class="code">return</code> in <samp class="file">trace.tmac</samp>. +</p></dd></dl> + + + +<ul class="mini-toc"> +<li><a href="Parameters.html" accesskey="1">Parameters</a></li> +<li><a href="Copy-Mode.html" accesskey="2">Copy Mode</a></li> +</ul> +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Page-Motions.html">Page Motions</a>, Previous: <a href="Conditionals-and-Loops.html">Conditionals and Loops</a>, Up: <a href="GNU-troff-Reference.html">GNU <code class="code">troff</code> Reference</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> |