diff options
Diffstat (limited to 'doc/groff.html.node/Setting-Registers.html')
| -rw-r--r-- | doc/groff.html.node/Setting-Registers.html | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/doc/groff.html.node/Setting-Registers.html b/doc/groff.html.node/Setting-Registers.html new file mode 100644 index 0000000..6fdf746 --- /dev/null +++ b/doc/groff.html.node/Setting-Registers.html @@ -0,0 +1,215 @@ +<!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>Setting Registers (The GNU Troff Manual)</title> + +<meta name="description" content="Setting Registers (The GNU Troff Manual)"> +<meta name="keywords" content="Setting Registers (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="Registers.html" rel="up" title="Registers"> +<link href="Interpolating-Registers.html" rel="next" title="Interpolating Registers"> +<link href="Registers.html" rel="prev" title="Registers"> +<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="subsection-level-extent" id="Setting-Registers"> +<div class="nav-panel"> +<p> +Next: <a href="Interpolating-Registers.html" accesskey="n" rel="next">Interpolating Registers</a>, Previous: <a href="Registers.html" accesskey="p" rel="prev">Registers</a>, Up: <a href="Registers.html" accesskey="u" rel="up">Registers</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="Setting-Registers-1">5.8.1 Setting Registers</h4> +<a class="index-entry-id" id="index-setting-registers-_0028nr_002c-_005cR_0029"></a> +<a class="index-entry-id" id="index-registers_002c-setting-_0028nr_002c-_005cR_0029"></a> + +<p>Define registers and update their values with the <code class="code">nr</code> request or +the <code class="code">\R</code> escape sequence. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002enr-1"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.nr</code></strong> <var class="def-var-arguments">ident value</var><a class="copiable-link" href='#index-_002enr-1'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-nr-1"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005cR_0027ident-value_0027"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\R<code class="code">'</code></code><span class="r"><i class="slanted">ident value</i></span><code class="t"><code class="code">'</code></code></strong><a class="copiable-link" href='#index-_005cR_0027ident-value_0027'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005cR"></a> +<p>Set register <var class="var">ident</var> to <var class="var">value</var>. If <var class="var">ident</var> doesn’t exist, +GNU <code class="code">troff</code> creates it. In the <code class="code">\R</code> escape sequence, the +delimiter need not be a neutral apostrophe; see <a class="ref" href="Delimiters.html">Delimiters</a>. It +also does not produce an input token in GNU <code class="code">troff</code>. See <a class="xref" href="Gtroff-Internals.html"><code class="code">gtroff</code> Internals</a>. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr a (((17 + (3 * 4))) % 4) +\n[a] +.\R'a (((17 + (3 * 4))) % 4)' +\n[a] + ⇒ 1 1 +</pre></div></div> + +<p>(Later, we will discuss additional forms of <code class="code">nr</code> and <code class="code">\R</code> that +can change a register’s value after it is dereferenced but before it is +interpolated. See <a class="xref" href="Auto_002dincrement.html">Auto-increment</a>.) +</p> +<p>The complete transparency of <code class="code">\R</code> can cause surprising effects if +you use registers like <code class="code">.k</code>, which get evaluated at the time they +are accessed. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.ll 1.6i +. +aaa bbb ccc ddd eee fff ggg hhh\R':k \n[.k]' +.tm :k == \n[:k] + ⇒ :k == 126950 +. +.br +. +aaa bbb ccc ddd eee fff ggg hhh\h'0'\R':k \n[.k]' +.tm :k == \n[:k] + ⇒ :k == 15000 +</pre></div></div> + +<p>If you process this with the PostScript device (<code class="code">-Tps</code>), there will +be a line break eventually after <code class="code">ggg</code> in both input lines. +However, after processing the space after <code class="code">ggg</code>, the partially +collected line is not overfull yet, so GNU <code class="code">troff</code> continues to +collect input until it sees the space (or in this case, the newline) +after <code class="code">hhh</code>. At this point, the line is longer than the line +length, and the line gets broken. +</p> +<p>In the first input line, since the <code class="code">\R</code> escape sequence leaves no +traces, the check for the overfull line hasn’t been done yet at the +point where <code class="code">\R</code> gets handled, and you get a value for the +<code class="code">.k</code> register that is even greater than the current line length. +</p> +<p>In the second input line, the insertion of <code class="code">\h'0'</code> to cause a +zero-width motion forces GNU <code class="code">troff</code> to check the line length, +which in turn causes the start of a new output line. Now <code class="code">.k</code> +returns the expected value. +</p></dd></dl> + +<p><code class="code">nr</code> and <code class="code">\R</code> each have two additional special forms to +increment or decrement a register. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002enr-2"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.nr</code></strong> <var class="def-var-arguments">ident <code class="t">+</code><span class="r"><i class="slanted">value</i></span></var><a class="copiable-link" href='#index-_002enr-2'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-nr-2"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002enr-3"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.nr</code></strong> <var class="def-var-arguments">ident <code class="t">-</code><span class="r"><i class="slanted">value</i></span></var><a class="copiable-link" href='#index-_002enr-3'> ¶</a></span></dt> +<dt class="deffnx def-cmd-deffn" id="index-_005cR_0027ident-_002bvalue_0027"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\R<code class="code">'</code></code><span class="r"><i class="slanted">ident <code class="t">+</code>value</i></span><code class="t"><code class="code">'</code></code></strong><a class="copiable-link" href='#index-_005cR_0027ident-_002bvalue_0027'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005cR-1"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005cR_0027ident-_002dvalue_0027"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\R<code class="code">'</code></code><span class="r"><i class="slanted">ident <code class="t">-</code>value</i></span><code class="t"><code class="code">'</code></code></strong><a class="copiable-link" href='#index-_005cR_0027ident-_002dvalue_0027'> ¶</a></span></dt> +<dd><p>Increment (decrement) register <var class="var">ident</var> by <var class="var">value</var>. In the +<code class="code">\R</code> escape sequence, the delimiter need not be a neutral +apostrophe; see <a class="ref" href="Delimiters.html">Delimiters</a>. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr a 1 +.nr a +1 +\na + ⇒ 2 +</pre></div></div> + +<a class="index-entry-id" id="index-negating-register-values"></a> +<p>A leading minus sign in <var class="var">value</var> is always interpreted as a +decrementation operator, not an algebraic sign. To assign a register a +negative value or the negated value of another register, you can +force GNU <code class="code">troff</code> to interpret ‘<samp class="samp">-</samp>’ as a negation or minus, +rather than decrementation, operator: enclose it with its operand in +parentheses or subtract it from zero. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr a 7 +.nr b 3 +.nr a -\nb +\na + ⇒ 4 +.nr a (-\nb) +\na + ⇒ -3 +.nr a 0-\nb +\na + ⇒ -3 +</pre></div></div> + +<p>If a register’s prior value does not exist (the register was undefined), +an increment or decrement is applied as if to 0. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002err"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.rr</code></strong> <var class="def-var-arguments">ident</var><a class="copiable-link" href='#index-_002err'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-rr"></a> +<a class="index-entry-id" id="index-removing-a-register-_0028rr_0029"></a> +<a class="index-entry-id" id="index-register_002c-removing-_0028rr_0029"></a> +<p>Remove register <var class="var">ident</var>. If <var class="var">ident</var> doesn’t exist, the request +is ignored. Technically, only the name is removed; the register’s +contents are still accessible under aliases created with <code class="code">aln</code>, if +any. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ernn"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.rnn</code></strong> <var class="def-var-arguments">ident1 ident2</var><a class="copiable-link" href='#index-_002ernn'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-rnn"></a> +<a class="index-entry-id" id="index-renaming-a-register-_0028rnn_0029"></a> +<a class="index-entry-id" id="index-register_002c-renaming-_0028rnn_0029"></a> +<p>Rename register <var class="var">ident1</var> to <var class="var">ident2</var>. If <var class="var">ident1</var> doesn’t +exist, the request is ignored. Renaming a built-in register does not +otherwise alter its properties. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ealn"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.aln</code></strong> <var class="def-var-arguments">new old</var><a class="copiable-link" href='#index-_002ealn'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-aln"></a> +<a class="index-entry-id" id="index-alias_002c-register_002c-creating-_0028aln_0029"></a> +<a class="index-entry-id" id="index-creating-alias-for-register-_0028aln_0029"></a> +<a class="index-entry-id" id="index-register_002c-creating-alias-for-_0028aln_0029"></a> +<p>Create an alias <var class="var">new</var> for an existing register <var class="var">old</var>, causing +the names to refer to the same stored object. If <var class="var">old</var> is +undefined, a warning in category ‘<samp class="samp">reg</samp>’ is produced and the request +is ignored. See <a class="xref" href="Warnings.html">Warnings</a>, for information about the enablement and +suppression of warnings. +</p> +<a class="index-entry-id" id="index-alias_002c-register_002c-removing-_0028rr_0029"></a> +<a class="index-entry-id" id="index-removing-alias-for-register-_0028rr_0029"></a> +<a class="index-entry-id" id="index-register_002c-removing-alias-for-_0028rr_0029"></a> +<p>To remove a register alias, invoke <code class="code">rr</code> on its name. A register’s +contents do not become inaccessible until it has no more names. +</p></dd></dl> + + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Interpolating-Registers.html">Interpolating Registers</a>, Previous: <a href="Registers.html">Registers</a>, Up: <a href="Registers.html">Registers</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> |