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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
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| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
| commit | d318611dd6f23fcfedd50e9b9e24620b102ba96a (patch) | |
| tree | 8b9eef82ca40fdd5a8deeabf07572074c236095d /doc/groff.html.node/Punning-Names.html | |
| parent | Initial commit. (diff) | |
| download | groff-upstream/1.23.0.tar.xz groff-upstream/1.23.0.zip | |
Adding upstream version 1.23.0.upstream/1.23.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
| -rw-r--r-- | doc/groff.html.node/Punning-Names.html | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/doc/groff.html.node/Punning-Names.html b/doc/groff.html.node/Punning-Names.html new file mode 100644 index 0000000..dde1a20 --- /dev/null +++ b/doc/groff.html.node/Punning-Names.html @@ -0,0 +1,190 @@ +<!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>Punning Names (The GNU Troff Manual)</title> + +<meta name="description" content="Punning Names (The GNU Troff Manual)"> +<meta name="keywords" content="Punning Names (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="Environments.html" rel="next" title="Environments"> +<link href="Diversions.html" rel="prev" title="Diversions"> +<style type="text/css"> +<!-- +div.example {margin-left: 3.2em} +kbd.key {font-style: normal} +--> +</style> + + +</head> + +<body lang="en"> +<div class="section-level-extent" id="Punning-Names"> +<div class="nav-panel"> +<p> +Next: <a href="Environments.html" accesskey="n" rel="next">Environments</a>, Previous: <a href="Diversions.html" accesskey="p" rel="prev">Diversions</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="Punning-Names-1">5.30 Punning Names</h3> +<a class="index-entry-id" id="index-diversions-1"></a> + +<p>Macros, strings, and diversions share a name space; recall +<a class="ref" href="Identifiers.html">Identifiers</a>. Internally, the same mechanism is used to store +them. You can thus call a macro with string interpolation syntax and +vice versa. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de subject +Typesetting +.. +.de predicate +rewards attention to detail +.. +\*[subject] \*[predicate]. +Truly. + ⇒ Typesetting + ⇒ rewards attention to detail Truly. +</pre></div></div> + +<p>What went wrong? Strings don’t contain newlines, but macros do. String +interpolation placed a newline at the end of ‘<samp class="samp">\*[subject]</samp>’, and the +next thing on the input was a space. Then when ‘<samp class="samp">\*[predicate]</samp>’ was +interpolated, it was followed by the empty request ‘<samp class="samp">.</samp>’ on a line by +itself. If we want to use macros as strings, we must take interpolation +behavior into account. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de subject +Typesetting\\ +.. +.de predicate +rewards attention to detail\\ +.. +\*[subject] \*[predicate]. +Truly. + ⇒ Typesetting rewards attention to detail. Truly. +</pre></div></div> + +<p>By ending each text line of the macros with an escaped +<code class="code">\<kbd class="key">RET</kbd></code>, we get the desired effect (see <a class="pxref" href="Line-Continuation.html">Line Continuation</a>).<a class="footnote" id="DOCF114" href="groff.html_fot.html#FOOT114"><sup>114</sup></a> +What would have happened if we had used only one backslash at a time +instead? +</p> +<p>Interpolating a string does not hide existing macro arguments. We can +also place the escaped newline outside the string interpolation instead +of within the string definition. Thus, in a macro, a more efficient way +of doing +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.xx \\$@ +</pre></div></div> + +<p>is +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">\\*[xx]\\ +</pre></div></div> + +<p>The latter calling syntax doesn’t change the value of <code class="code">\$0</code>, which +is then inherited from the calling macro (see <a class="pxref" href="Parameters.html">Parameters</a>). +</p> +<p>Diversions can be also called with string syntax. It is sometimes +convenient to copy one-line diversions to a string. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.di xx +the +.ft I +interpolation system +.ft +.br +.di +.ds yy This is a test of \*(xx\c +\*(yy. + ⇒ This is a test of the <i class="i">interpolation system</i>. +</pre></div></div> + +<p>As the previous example shows, it is possible to store formatted output +in strings. The <code class="code">\c</code> escape sequence prevents the subsequent +newline from being interpreted as a break (again, +see <a class="pxref" href="Line-Continuation.html">Line Continuation</a>). +</p> +<p>Copying multi-output line diversions produces unexpected results. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.di xxx +a funny +.br +test +.br +.di +.ds yyy This is \*[xxx]\c +\*[yyy]. + ⇒ test This is a funny. +</pre></div></div> + +<p>Usually, it is not predictable whether a diversion contains one or more +output lines, so this mechanism should be avoided. With <abbr class="acronym">AT&T</abbr> +<code class="code">troff</code>, this was the only solution to strip off a final newline +from a diversion. Another disadvantage is that the spaces in the copied +string are already formatted, preventing their adjustment. This can +cause ugly results. +</p> +<a class="index-entry-id" id="index-stripping-final-newline-in-diversions"></a> +<a class="index-entry-id" id="index-diversion_002c-stripping-final-newline"></a> +<a class="index-entry-id" id="index-final-newline_002c-stripping-in-diversions"></a> +<a class="index-entry-id" id="index-newline_002c-final_002c-stripping-in-diversions"></a> +<a class="index-entry-id" id="index-horizontal-space_002c-unformatting"></a> +<a class="index-entry-id" id="index-space_002c-horizontal_002c-unformatting"></a> +<a class="index-entry-id" id="index-unformatting-horizontal-space"></a> +<p>A clean solution to this problem is available in GNU <code class="code">troff</code>, using +the requests <code class="code">chop</code> to remove the final newline of a diversion, and +<code class="code">unformat</code> to make the horizontal spaces adjustable again. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.box xxx +a funny +.br +test +.br +.box +.chop xxx +.unformat xxx +This is \*[xxx]. + ⇒ This is a funny test. +</pre></div></div> + +<p>See <a class="xref" href="Gtroff-Internals.html"><code class="code">gtroff</code> Internals</a>. +</p> + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Environments.html">Environments</a>, Previous: <a href="Diversions.html">Diversions</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> |