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<html>
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<title>Generator Directives Controlling the Maximum Field Width (maxwidth[])</title>
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<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.karma.reference.directive.maxwidth"></a><a class="link" href="maxwidth.html" title="Generator Directives Controlling the Maximum Field Width (maxwidth[])">Generator
Directives Controlling the Maximum Field Width (<code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[]</span></code>)</a>
</h5></div></div></div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h0"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.description"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.description">Description</a>
</h6>
<p>
The <code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[]</span></code>
directive allows to limit (truncate) the overall length of the output
generated by the embedded generator.
</p>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h1"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.header"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.header">Header</a>
</h6>
<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/karma/directive/maxwidth.hpp></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma_maxwidth</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
</pre>
<p>
Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>.
</p>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
Name
</p>
</th></tr></thead>
<tbody><tr><td>
<p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">maxwidth</span> <span class="comment">//
alias: boost::spirit::karma::maxwidth</span></code>
</p>
</td></tr></tbody>
</table></div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h2"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.model_of"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.model_of">Model of</a>
</h6>
<div class="blockquote"><blockquote class="blockquote"><p>
<a class="link" href="../generator_concepts/unarygenerator.html" title="UnaryGenerator"><code class="computeroutput"><span class="identifier">UnaryGenerator</span></code></a>
</p></blockquote></div>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">a</span></code></span></dt>
<dd><p>
A generator object
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">A</span></code></span></dt>
<dd><p>
Attribute type of the generator <code class="computeroutput"><span class="identifier">a</span></code>
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">num</span></code></span></dt>
<dd><p>
Numeric literal, any unsigned integer value, or a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy
Argument</a> that evaluates to an unsigned integer value
</p></dd>
</dl>
</div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h3"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.expression_semantics"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.expression_semantics">Expression
Semantics</a>
</h6>
<p>
Semantics of an expression is defined only where it differs from, or
is not defined in <a class="link" href="../generator_concepts/unarygenerator.html" title="UnaryGenerator"><code class="computeroutput"><span class="identifier">UnaryGenerator</span></code></a>.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
Limit the overall length of the emitted output of the embedded
generator (including characters generated by automatic delimiting)
to the number of characters as defined by the preprocessor
constant <code class="computeroutput"><span class="identifier">BOOST_KARMA_DEFAULT_FIELD_MAXWIDTH</span></code>.
Any additional output is truncated. The directive succeeds
as long as the embedded generator succeeded (unless the underlying
output stream reports an error).
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
Limit the overall length of the emitted output of the embedded
generator (including characters generated by automatic delimiting)
to the number of characters as defined by <code class="computeroutput"><span class="identifier">num</span></code>.
Any additional output is truncated. The directive succeeds
as long as the embedded generator succeeded (unless the underlying
output stream reports an error).
</p>
</td>
</tr>
</tbody>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top">
<p>
The <code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[]</span></code>
generator directive does not pad the generated output to fill the specified
column width. If the emitted output is shorter than the specified (or
implied) column width, the generated output will be more narrow than
the column width.
</p>
<p>
If the output needs to always be equal to a specified column width,
use one of the alignment directives <code class="computeroutput"><span class="identifier">left</span><span class="special">-</span><span class="identifier">align</span><span class="special">[]</span></code>, <code class="computeroutput"><span class="identifier">center</span><span class="special">[]</span></code>, or <code class="computeroutput"><span class="identifier">right_align</span><span class="special">[]</span></code>, for instance:
</p>
<pre class="programlisting"><span class="identifier">maxwidth</span><span class="special">(</span><span class="number">8</span><span class="special">)[</span><span class="identifier">left_align</span><span class="special">(</span><span class="number">8</span><span class="special">)[</span><span class="string">"1234"</span><span class="special">]]</span>
</pre>
<p>
which will output: <code class="computeroutput"><span class="string">"1234 "</span></code>
(without the quotes).
</p>
</td></tr>
</table></div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h4"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.attributes"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.attributes">Attributes</a>
</h6>
<p>
See <a class="link" href="../../quick_reference/compound_attribute_rules.html#spirit.karma.quick_reference.compound_attribute_rules.notation">Compound
Attribute Notation</a>.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Attribute
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">maxwidth</span><span class="special">[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span>
<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">maxwidth</span><span class="special">[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
<p>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">maxwidth</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span>
<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">maxwidth</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
<p>
</p>
</td>
</tr>
</tbody>
</table></div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h5"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.complexity"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.complexity">Complexity</a>
</h6>
<div class="blockquote"><blockquote class="blockquote"><p>
The overall complexity of the generator directive <code class="computeroutput"><span class="identifier">maxwidth</span><span class="special">[]</span></code> is defined by the complexity of its
embedded generator. The complexity of the directive itself is O(N),
where <code class="computeroutput"><span class="identifier">N</span></code> is the number
of characters generated by the maxwidth directive.
</p></blockquote></div>
<h6>
<a name="spirit.karma.reference.directive.maxwidth.h6"></a>
<span><a name="spirit.karma.reference.directive.maxwidth.example"></a></span><a class="link" href="maxwidth.html#spirit.karma.reference.directive.maxwidth.example">Example</a>
</h6>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.karma.reference.basics.examples">Basics Examples</a>
section.
</p></td></tr>
</table></div>
<p>
Some includes:
</p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span>
</pre>
<p>
</p>
<p>
Some using declarations:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">maxwidth</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">left_align</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">right_align</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
Basic usage of <code class="computeroutput"><span class="identifier">maxwidth</span></code>
generator directive:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">test_generator</span><span class="special">(</span><span class="string">"01234"</span><span class="special">,</span> <span class="identifier">maxwidth</span><span class="special">(</span><span class="number">5</span><span class="special">)[</span><span class="string">"0123456789"</span><span class="special">]);</span>
<span class="identifier">test_generator</span><span class="special">(</span><span class="string">" 012"</span><span class="special">,</span> <span class="identifier">maxwidth</span><span class="special">(</span><span class="number">5</span><span class="special">)[</span><span class="identifier">right_align</span><span class="special">(</span><span class="number">12</span><span class="special">)[</span><span class="string">"0123456789"</span><span class="special">]]);</span>
<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"0123 "</span><span class="special">,</span> <span class="identifier">maxwidth</span><span class="special">(</span><span class="number">8</span><span class="special">)[</span><span class="identifier">left_align</span><span class="special">(</span><span class="number">8</span><span class="special">)[</span><span class="string">"0123"</span><span class="special">]]);</span>
</pre>
<p>
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
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