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<div class="section" title="Real Number Generators (float_, double_, etc.)">
<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.karma.reference.numeric.real_number"></a><a class="link" href="real_number.html" title="Real Number Generators (float_, double_, etc.)"> Real
Number Generators (<code class="computeroutput"><span class="identifier">float_</span></code>,
<code class="computeroutput"><span class="identifier">double_</span></code>, etc.)</a>
</h5></div></div></div>
<a name="spirit.karma.reference.numeric.real_number.description"></a><h6>
<a name="id888601"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.description">Description</a>
</h6>
<p>
The <code class="computeroutput"><span class="identifier">real_generator</span></code> can
generate real numbers of arbitrary length and size limited by its template
parameter, <code class="computeroutput"><span class="identifier">Num</span></code>. The numeric
base type <code class="computeroutput"><span class="identifier">Num</span></code> can be
a user defined numeric type such as fixed_point (fixed point reals) and
bignum (unlimited precision numbers) if the type follows certain expression
requirements (for more information about the requirements, see <a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.additional_requirements">below</a>).
</p>
<a name="spirit.karma.reference.numeric.real_number.header"></a><h6>
<a name="id888644"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.header">Header</a>
</h6>
<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/karma/numeric/real.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_real</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>
<a name="spirit.karma.reference.numeric.real_number.namespace"></a><h6>
<a name="id888718"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.namespace">Namespace</a>
</h6>
<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">lit</span> <span class="comment">// alias:
boost::spirit::karma::lit</span></code>
</p>
</td></tr>
<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">float_</span> <span class="comment">// alias:
boost::spirit::karma::float_</span></code>
</p>
</td></tr>
<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">double_</span> <span class="comment">//
alias: boost::spirit::karma::double_</span></code>
</p>
</td></tr>
<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">long_double</span> <span class="comment">//
alias: boost::spirit::karma::long_double</span></code>
</p>
</td></tr>
</tbody>
</table></div>
<div class="note" title="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>
<code class="computeroutput"><span class="identifier">lit</span></code> is reused by the
<a class="link" href="../string.html" title="String">String Generators</a>,
the <a class="link" href="../char.html" title="Char">Character Generators</a>,
and the Numeric Generators. In general, a char generator is created
when you pass in a character, a string generator is created when you
pass in a string, and a numeric generator is created when you use a
numeric literal.
</p></td></tr>
</table></div>
<a name="spirit.karma.reference.numeric.real_number.synopsis"></a><h6>
<a name="id888935"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.synopsis">Synopsis</a>
</h6>
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Num</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">RealPolicies</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">real_generator</span><span class="special">;</span>
</pre>
<a name="spirit.karma.reference.numeric.real_number.template_parameters"></a><h6>
<a name="id889003"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.template_parameters">Template
parameters</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Parameter
</p>
</th>
<th>
<p>
Description
</p>
</th>
<th>
<p>
Default
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Num</span></code>
</p>
</td>
<td>
<p>
The type of the real number to generate.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">double</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">RealPolicies</span></code>
</p>
</td>
<td>
<p>
The policies to use while converting the real number.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">real_policies</span><span class="special"><</span><span class="identifier">Num</span><span class="special">></span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
For more information about the type <code class="computeroutput"><span class="identifier">RealPolicies</span></code>
see <a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.real_number_formatting_policies">below</a>.
</p>
<a name="spirit.karma.reference.numeric.real_number.model_of"></a><h6>
<a name="id889159"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.model_of">Model
of</a>
</h6>
<div class="blockquote"><blockquote class="blockquote">
<p>
</p>
<p>
<a class="link" href="../generator_concepts/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</span></code></a>
</p>
<p>
</p>
</blockquote></div>
<div class="variablelist" title="Notation">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">num</span></code></span></dt>
<dd><p>
Numeric literal, any real number value, or a <a class="link" href="../karma_basics.html#spirit.karma.reference.karma_basics.lazy_argument">Lazy
Argument</a> that evaluates to a real number value of type <code class="computeroutput"><span class="identifier">Num</span></code>
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">Num</span></code></span></dt>
<dd><p>
Type of <code class="computeroutput"><span class="identifier">num</span></code>: any
real number type
</p></dd>
</dl>
</div>
<a name="spirit.karma.reference.numeric.real_number.expression_semantics"></a><h6>
<a name="id889261"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.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/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</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">lit</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Generate the real number literal <code class="computeroutput"><span class="identifier">num</span></code>
using the default formatting (no trailing zeros, <code class="computeroutput"><span class="identifier">fixed</span></code> representation for numbers
<code class="computeroutput"><span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span>
<span class="special"><=</span> <span class="number">1e5</span>
<span class="special">&&</span> <span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special">></span>
<span class="number">1e-3</span></code>, scientific representation
otherwise, 3 fractional digits, sign is only printed for negative
literals). This generator never fails (unless the underlying
output stream reports an error).
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">float_</span>
<span class="identifier">double_</span>
<span class="identifier">long_double</span></pre>
<p>
</p>
</td>
<td>
<p>
Generate the real number provided by a mandatory attribute using
the default formatting (no trailing zeros, <code class="computeroutput"><span class="identifier">fixed</span></code>
representation for numbers <code class="computeroutput"><span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special"><=</span>
<span class="number">1e5</span> <span class="special">&&</span>
<span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span>
<span class="special">></span> <span class="number">1e-3</span></code>,
scientific representation otherwise, 3 fractional digits, sign
is only printed for negative literals). This generator never
fails (unless the underlying output stream reports an error).
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">float_</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span>
<span class="identifier">double_</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span>
<span class="identifier">long_double</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></pre>
<p>
</p>
</td>
<td>
<p>
Generate the real point number provided by the immediate literal
value the generator is initialized from using the default formatting
(no trailing zeros, <code class="computeroutput"><span class="identifier">fixed</span></code>
representation for numbers <code class="computeroutput"><span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special"><=</span>
<span class="number">1e5</span> <span class="special">&&</span>
<span class="identifier">fabs</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span>
<span class="special">></span> <span class="number">1e-3</span></code>,
scientific representation otherwise, 3 fractional digits, sign
is only printed for negative literals). If this generator has
an associated attribute it succeeds only if the attribute is
equal to the immediate literal (unless the underlying output
stream reports an error). Otherwise this generator fails and
does not generate any output.
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
All generators listed in the table above (except <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>) are predefined specializations of the
<code class="computeroutput"><span class="identifier">real_generator</span><span class="special"><</span><span class="identifier">Num</span><span class="special">,</span> <span class="identifier">RealPolicies</span><span class="special">></span></code>
basic real number generator type described below. It is possible to directly
use this type to create real number generators using a wide range of
formatting options.
</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>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">real_generator</span><span class="special"><</span>
<span class="identifier">Num</span><span class="special">,</span> <span class="identifier">RealPolicies</span>
<span class="special">>()</span></pre>
<p>
</p>
</td>
<td>
<p>
Generate the real number of type <code class="computeroutput"><span class="identifier">Num</span></code>
provided by a mandatory attribute using the specified <code class="computeroutput"><span class="identifier">RealPolicies</span></code>. This generator
never fails (unless the underlying output stream reports an error).
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">real_generator</span><span class="special"><</span>
<span class="identifier">Num</span><span class="special">,</span> <span class="identifier">RealPolicies</span>
<span class="special">>()(</span><span class="identifier">num</span><span class="special">)</span></pre>
<p>
</p>
</td>
<td>
<p>
Generate the real number of type <code class="computeroutput"><span class="identifier">Num</span></code>
provided by the immediate literal value the generator is initialized
from using the specified <code class="computeroutput"><span class="identifier">RealPolicies</span></code>.
If this generator has an associated attribute it succeeds only
if the attribute is equal to the immediate literal (unless the
underlying output stream reports an error). Otherwise this generator
fails and does not generate any output.
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="spirit.karma.reference.numeric.real_number.additional_requirements"></a><h6>
<a name="id891041"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.additional_requirements">Additional
Requirements</a>
</h6>
<p>
The following list enumerates the requirements which must be met in order
to use a certain type <code class="computeroutput"><span class="identifier">Num</span></code>
to instantiate a <code class="computeroutput"><span class="identifier">real_generator</span><span class="special"><</span><span class="identifier">Num</span><span class="special">,</span> <span class="identifier">Policies</span><span class="special">></span></code>.
</p>
<p>
In order to be usable as the first template parameter for <code class="computeroutput"><span class="identifier">real_generator</span><span class="special"><></span></code>
the type <code class="computeroutput"><span class="identifier">Num</span></code> must have
defined:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
comparison operators for: <code class="computeroutput"><span class="special"><</span></code>,
<code class="computeroutput"><span class="special"><=</span></code>, <code class="computeroutput"><span class="special">==</span></code>,
<code class="computeroutput"><span class="special">!=</span></code>, <code class="computeroutput"><span class="special">></span></code>,
and <code class="computeroutput"><span class="special">>=</span></code>
</li>
<li class="listitem">
numeric operators for: <code class="computeroutput"><span class="special">+</span></code>,
<code class="computeroutput"><span class="special">-</span></code>, <code class="computeroutput"><span class="special">/</span></code>,
<code class="computeroutput"><span class="special">*</span></code>, and <code class="computeroutput"><span class="special">%</span></code>
</li>
<li class="listitem">
functions implementing the interface and the semantics of: <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">fmod</span></code>, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pow</span></code>,
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">log10</span></code>, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">lround</span></code>,
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ltrunc</span></code>, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">modf</span></code>,
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">floor</span></code>, and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ceil</span></code>.
These need to be defined in a way so that they will be found using
argument dependent lookup (ADL).
</li>
<li class="listitem">
a valid specialization of the type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">Num</span><span class="special">></span></code> allowing for numeric property inspection.
</li>
</ul></div>
<a name="spirit.karma.reference.numeric.real_number.attributes"></a><h6>
<a name="id891350"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.attributes">Attributes</a>
</h6>
<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">lit</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">unused</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">float_</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">float</span></code>, attribute
is mandatory (otherwise compilation will fail)
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">float_</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">float_</span></code>, attribute
is optional, if it is supplied, the generator compares the attribute
with <code class="computeroutput"><span class="identifier">num</span></code> and
succeeds only if both are equal, failing otherwise.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">double_</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">double</span></code>, attribute
is mandatory (otherwise compilation will fail)
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">double_</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">double</span></code>, attribute
is optional, if it is supplied, the generator compares the attribute
with <code class="computeroutput"><span class="identifier">num</span></code> and
succeeds only if both are equal, failing otherwise.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">long_double</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>,
attribute is mandatory (otherwise compilation will fail)
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">long_double</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>,
attribute is optional, if it is supplied, the generator compares
the attribute with <code class="computeroutput"><span class="identifier">num</span></code>
and succeeds only if both are equal, failing otherwise.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">real_generator</span><span class="special"><</span>
<span class="identifier">Num</span><span class="special">,</span> <span class="identifier">Policies</span>
<span class="special">>()</span></pre>
<p>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">Num</span></code>, attribute
is mandatory (otherwise compilation will fail)
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">real_generator</span><span class="special"><</span>
<span class="identifier">Num</span><span class="special">,</span> <span class="identifier">Policies</span>
<span class="special">>()(</span><span class="identifier">num</span><span class="special">)</span></pre>
<p>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">Num</span></code>, attribute
is optional, if it is supplied, the generator compares the attribute
with <code class="computeroutput"><span class="identifier">num</span></code> and
succeeds only if both are equal, failing otherwise.
</p>
</td>
</tr>
</tbody>
</table></div>
<div class="note" title="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>
In addition to their usual attribute of type <code class="computeroutput"><span class="identifier">Num</span></code>
all listed generators accept an instance of a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><</span><span class="identifier">Num</span><span class="special">></span></code> as well. If the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><></span></code> is initialized (holds a value)
the generators behave as if their attribute was an instance of <code class="computeroutput"><span class="identifier">Num</span></code> and emit the value stored in
the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><></span></code>.
Otherwise the generators will fail.
</p></td></tr>
</table></div>
<a name="spirit.karma.reference.numeric.real_number.real_number_formatting_policies"></a><h6>
<a name="id891895"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.real_number_formatting_policies">Real
Number Formatting Policies</a>
</h6>
<p>
If special formatting of a real number is needed, overload the policy
class <code class="computeroutput"><span class="identifier">real_policies</span><span class="special"><</span><span class="identifier">Num</span><span class="special">></span></code>
and use it as a template parameter to the <code class="computeroutput"><span class="identifier">real_generator</span><span class="special"><></span></code> real number generator. For instance:
</p>
<pre class="programlisting"><span class="comment">// define a new real number formatting policy
</span><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Num</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">scientific_policy</span> <span class="special">:</span> <span class="identifier">real_policies</span><span class="special"><</span><span class="identifier">Num</span><span class="special">></span>
<span class="special">{</span>
<span class="comment">// we want the numbers always to be in scientific format
</span> <span class="keyword">static</span> <span class="keyword">int</span> <span class="identifier">floatfield</span><span class="special">(</span><span class="identifier">Num</span> <span class="identifier">n</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">fmtflags</span><span class="special">::</span><span class="identifier">scientific</span><span class="special">;</span> <span class="special">}</span>
<span class="special">};</span>
<span class="comment">// define a new generator type based on the new policy
</span><span class="keyword">typedef</span> <span class="identifier">real_generator</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">scientific_policy</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="special">></span> <span class="identifier">science_type</span><span class="special">;</span>
<span class="identifier">science_type</span> <span class="keyword">const</span> <span class="identifier">scientific</span> <span class="special">=</span> <span class="identifier">science_type</span><span class="special">();</span>
<span class="comment">// use the new generator
</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">science_type</span><span class="special">(),</span> <span class="number">1.0</span><span class="special">);</span> <span class="comment">// will output: 1.0e00
</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">scientific</span><span class="special">,</span> <span class="number">0.1</span><span class="special">);</span> <span class="comment">// will output: 1.0e-01
</span></pre>
<p>
The template parameter <code class="computeroutput"><span class="identifier">Num</span></code>
should be the type to be formatted using the overloaded policy type.
At the same time <code class="computeroutput"><span class="identifier">Num</span></code>
will be used as the attribute type of the created real number generator.
</p>
<a name="spirit.karma.reference.numeric.real_number.real_number_formatting_policy_expression_semantics"></a><h6>
<a name="id892249"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.real_number_formatting_policy_expression_semantics">Real
Number Formatting Policy Expression Semantics</a>
</h6>
<p>
A real number formatting policy should expose the following variables
and functions:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Inserter</span>
<span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span>
<span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Policies</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">call</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span>
<span class="special">,</span> <span class="identifier">Policies</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">p</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This is the main function used to generate the output for a real
number. It is called by the real generator in order to perform
the conversion. In theory all of the work can be implemented
here, but the easiest way is to use existing functionality provided
by the type specified by the template parameter <code class="computeroutput"><span class="identifier">Inserter</span></code>. The default implementation
of this functions is:
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Inserter</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span>
<span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Policies</span><span class="special">></span>
<span class="keyword">static</span> <span class="keyword">bool</span>
<span class="identifier">call</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">Policies</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">p</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">Inserter</span><span class="special">::</span><span class="identifier">call_n</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">p</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the real
number to convert
</p>
<p>
<code class="computeroutput"><span class="identifier">p</span></code> is the instance
of the policy type used to instantiate this real number generator.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">bool</span> <span class="identifier">force_sign</span><span class="special">(</span><span class="identifier">Num</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
The default behavior is to not to require generating a sign.
If the function <code class="computeroutput"><span class="identifier">force_sign</span><span class="special">()</span></code> returns true, then all generated
numbers will have a sign (<code class="computeroutput"><span class="char">'+'</span></code>
or <code class="computeroutput"><span class="char">'-'</span></code>, zeros will
have a space instead of a sign).
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the real
number to output. This can be used to adjust the required behavior
depending on the value of this number.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">bool</span> <span class="identifier">trailing_zeros</span><span class="special">(</span><span class="identifier">Num</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
Return whether trailing zero digits have to be emitted in the
fractional part of the output. If set, this flag instructs the
real number generator to emit trailing zeros up to the required
precision digits (as returned by the <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> function).
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the real
number to output. This can be used to adjust the required behavior
depending on the value of this number.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">int</span> <span class="identifier">floatfield</span><span class="special">(</span><span class="identifier">Num</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
Decide, which representation type to use in the generated output.
</p>
<p>
By default all numbers having an absolute value of zero or in
between <code class="computeroutput"><span class="number">0.001</span></code> and
<code class="computeroutput"><span class="number">100000</span></code> will be generated
using the fixed format, all others will be generated using the
scientific representation.
</p>
<p>
The <code class="computeroutput"><span class="identifier">trailing_zeros</span><span class="special">()</span></code> can be used to force the output
of trailing zeros in the fractional part up to the number of
digits returned by the <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> member function. The default
is not to generate the trailing zeros.
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the real
number to output. This can be used to adjust the formatting flags
depending on the value of this number.
</p>
<p>
The return value has to be either <code class="computeroutput"><span class="identifier">fmtflags</span><span class="special">::</span><span class="identifier">scientific</span></code>
(generate real number values in scientific notation) or <code class="computeroutput"><span class="identifier">fmtflags</span><span class="special">::</span><span class="identifier">fixed</span></code> (generate real number
values in fixed-point notation).
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">unsigned</span> <span class="identifier">precision</span><span class="special">(</span><span class="identifier">Num</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
Return the maximum number of decimal digits to generate in the
fractional part of the output.
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the real
number to output. This can be used to adjust the required precision
depending on the value of this number. If the trailing zeros
flag is specified the fractional part of the output will be 'filled'
with zeros, if appropriate.
</p>
<p>
<span class="bold"><strong>Note:</strong></span> If the trailing_zeros
flag is not in effect additional semantics apply. See the description
for the <code class="computeroutput"><span class="identifier">fraction_part</span><span class="special">()</span></code> function below. Moreover, this
precision will be limited to the value of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">digits10</span>
<span class="special">+</span> <span class="number">1</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">bool</span> <span class="identifier">ForceSign</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">integer_part</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span>
<span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">sign</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">force_sign</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called to generate the integer part of the real
number.
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the absolute
value of the integer part of the real number to convert (always
non-negative)
</p>
<p>
<code class="computeroutput"><span class="identifier">sign</span></code> is the sign
of the overall real number to convert.
</p>
<p>
<code class="computeroutput"><span class="identifier">force_sign</span></code> is
a flag indicating whether a sign has to be generated even for
non-negative numbers (this is the same as has been returned from
the function <code class="computeroutput"><span class="identifier">force_sign</span><span class="special">()</span></code> described above)
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">dot</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span><span class="special">,</span>
<span class="keyword">unsigned</span> <span class="identifier">precision</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called to generate the decimal point.
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the fractional
part of the real number to convert. Note that this number is
scaled such, that it represents the number of units which correspond
to the value returned from the <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> function earlier. I.e. a fractional
part of <code class="computeroutput"><span class="number">0.01234</span></code> is
represented as <code class="computeroutput"><span class="number">1234</span></code>
when the function <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> returned <code class="computeroutput"><span class="number">5</span></code>.
</p>
<p>
<code class="computeroutput"><span class="identifier">precision</span></code> is
the number of digits to emit as returned by the function <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code>
described above
</p>
<p>
This is given to allow to decide, whether a decimal point has
to be generated at all.
</p>
<p>
<span class="bold"><strong>Note:</strong></span> If the <code class="computeroutput"><span class="identifier">trailing_zeros</span></code>
flag is not in effect additional comments apply. See the description
for the <code class="computeroutput"><span class="identifier">fraction_part</span><span class="special">()</span></code> function below.
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">fraction_part</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span>
<span class="special">,</span> <span class="keyword">unsigned</span> <span class="identifier">adjprec</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="identifier">precision</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called to generate the fractional part of the
number.
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the fractional
part of the real number to convert. Note that this number is
scaled such, that it represents the number of units which correspond
to the value returned from the <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> function earlier. I.e. a fractional
part of <code class="computeroutput"><span class="number">0.01234</span></code> is
represented as <code class="computeroutput"><span class="number">1234</span></code>
when the function <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> returned <code class="computeroutput"><span class="number">5</span></code>.
</p>
<p>
<code class="computeroutput"><span class="identifier">adjprec</span></code> is the
corrected number of digits to emit (see note below)
</p>
<p>
<code class="computeroutput"><span class="identifier">precision</span></code> is
the number of digits to emit as returned by the function <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code>
described above
</p>
<p>
<span class="bold"><strong>Note:</strong></span> If <code class="computeroutput"><span class="identifier">trailing_zeros</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="keyword">false</span></code>
the <code class="computeroutput"><span class="identifier">adjprec</span></code> parameter
will have been corrected from the value the <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> function returned earlier (defining
the maximal number of fractional digits) in the sense, that it
takes into account trailing zeros. I.e. a real number <code class="computeroutput"><span class="number">0.0123</span></code> and a value of <code class="computeroutput"><span class="number">5</span></code> returned from <code class="computeroutput"><span class="identifier">precision</span><span class="special">()</span></code> will result in:
</p>
<p>
<code class="computeroutput"><span class="identifier">trailing_zeros</span><span class="special">()</span></code> returned <code class="computeroutput"><span class="keyword">false</span></code>:
<code class="computeroutput"><span class="identifier">n</span></code> will be <code class="computeroutput"><span class="number">123</span></code>, and <code class="computeroutput"><span class="identifier">adjprec</span></code>
will be <code class="computeroutput"><span class="number">4</span></code> (as we
need to print <code class="computeroutput"><span class="number">0123</span></code>)
</p>
<p>
<code class="computeroutput"><span class="identifier">trailing_zeros</span><span class="special">()</span></code> returned <code class="computeroutput"><span class="keyword">true</span></code>:
<code class="computeroutput"><span class="identifier">n</span></code> will be <code class="computeroutput"><span class="number">1230</span></code>, and <code class="computeroutput"><span class="identifier">adjprec</span></code>
will be <code class="computeroutput"><span class="number">5</span></code> (as we
need to print <code class="computeroutput"><span class="number">01230</span></code>)
</p>
<p>
The missing preceding zeros in the fractional part have to be
supplied by the implementation of this policy function.
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">Tag</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">exponent</span><span class="special">(</span>
<span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="keyword">long</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called to generate the exponential part of the
number (this is called only if the <code class="computeroutput"><span class="identifier">floatfield</span><span class="special">()</span></code> function returned the <code class="computeroutput"><span class="identifier">fmtflags</span><span class="special">::</span><span class="identifier">scientific</span></code> flag).
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the (signed)
exponential part of the real number to convert.
</p>
<p>
The template parameters <code class="computeroutput"><span class="identifier">CharEncoding</span></code>
and <code class="computeroutput"><span class="identifier">Tag</span></code> are either
of the type <code class="computeroutput"><span class="identifier">unused_type</span></code>
or describe the character class and conversion to be applied
to any output possibly influenced by either the <code class="computeroutput"><span class="identifier">lower</span><span class="special">[]</span></code>
or <code class="computeroutput"><span class="identifier">upper</span><span class="special">[]</span></code>
directives.
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span>
<span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Tag</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">nan</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span>
<span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">force_sign</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called whenever the number to print is a non-normal
real number of type <code class="computeroutput"><span class="identifier">NaN</span></code>.
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the (signed)
real number to convert
</p>
<p>
<code class="computeroutput"><span class="identifier">force_sign</span></code> is
a flag indicating whether a sign has to be generated even for
non-negative numbers (this is the same as has been returned from
the function <code class="computeroutput"><span class="identifier">force_sign</span><span class="special">()</span></code> described above)
</p>
<p>
The template parameters <code class="computeroutput"><span class="identifier">CharEncoding</span></code>
and <code class="computeroutput"><span class="identifier">Tag</span></code> are either
of the type <code class="computeroutput"><span class="identifier">unused_type</span></code>
or describe the character class and conversion to be applied
to any output possibly influenced by either the <code class="computeroutput"><span class="identifier">lower</span><span class="special">[]</span></code>
or <code class="computeroutput"><span class="identifier">upper</span><span class="special">[]</span></code>
directives.
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span>
<span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Tag</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
<span class="keyword">bool</span> <span class="identifier">inf</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span>
<span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">force_sign</span><span class="special">);</span>
</pre>
<p>
</p>
</td>
<td>
<p>
This function is called whenever the number to print is a non-normal
real number of type <code class="computeroutput"><span class="identifier">Inf</span></code>.
</p>
<p>
<code class="computeroutput"><span class="identifier">sink</span></code> is the output
iterator to use for generation
</p>
<p>
<code class="computeroutput"><span class="identifier">n</span></code> is the (signed)
real number to convert
</p>
<p>
<code class="computeroutput"><span class="identifier">force_sign</span></code> is
a flag indicating whether a sign has to be generated even for
non-negative numbers (this is the same as has been returned from
the function <code class="computeroutput"><span class="identifier">force_sign</span><span class="special">()</span></code> described above)
</p>
<p>
The template parameters <code class="computeroutput"><span class="identifier">CharEncoding</span></code>
and <code class="computeroutput"><span class="identifier">Tag</span></code> are either
of the type <code class="computeroutput"><span class="identifier">unused_type</span></code>
or describe the character class and conversion to be applied
to any output possibly influenced by either the <code class="computeroutput"><span class="identifier">lower</span><span class="special">[]</span></code>
or <code class="computeroutput"><span class="identifier">upper</span><span class="special">[]</span></code>
directives.
</p>
<p>
The return value defines the outcome of the whole generator.
If it is <code class="computeroutput"><span class="keyword">false</span></code>,
no further output is generated, immediately returning <code class="computeroutput"><span class="keyword">false</span></code> from the calling <code class="computeroutput"><span class="identifier">real_generator</span></code> as well. If
it is <code class="computeroutput"><span class="keyword">true</span></code>, normal
output generation continues.
</p>
</td>
</tr>
</tbody>
</table></div>
<div class="tip" title="Tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top"><p>
The easiest way to implement a proper real number formatting policy
is to derive a new type from the the type <code class="computeroutput"><span class="identifier">real_policies</span><span class="special"><></span></code> while overriding the aspects
of the formatting which need to be changed.
</p></td></tr>
</table></div>
<a name="spirit.karma.reference.numeric.real_number.complexity"></a><h6>
<a name="id894993"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.complexity">Complexity</a>
</h6>
<div class="blockquote"><blockquote class="blockquote">
<p>
</p>
<p>
O(N), where <code class="computeroutput"><span class="identifier">N</span></code> is
the number of digits needed to represent the generated real number.
</p>
<p>
</p>
</blockquote></div>
<a name="spirit.karma.reference.numeric.real_number.example"></a><h6>
<a name="id895024"></a>
<a class="link" href="real_number.html#spirit.karma.reference.numeric.real_number.example">Example</a>
</h6>
<div class="note" title="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="../karma_basics.html#spirit.karma.reference.karma_basics.examples">Basics Examples</a>
section.
</p></td></tr>
</table></div>
<p>
Some includes:
</p>
<p>
</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">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">phoenix_core</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">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">phoenix_operator</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">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">std_pair</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>
</p>
<p>
Some using declarations:
</p>
<p>
</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">lit</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
</p>
<p>
Basic usage of an <code class="computeroutput"><span class="identifier">double_</span></code>
generator:
</p>
<p>
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">test_generator</span><span class="special">(</span><span class="string">"2.0"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="number">2.0</span><span class="special">));</span>
<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"2.0"</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"2.0"</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">(</span><span class="number">2.0</span><span class="special">),</span> <span class="number">2.0</span><span class="special">);</span>
<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">""</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">(</span><span class="number">2.0</span><span class="special">),</span> <span class="number">3.0</span><span class="special">);</span> <span class="comment">// fails (as 2.0 != 3.0)!
</span><span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"-2.0"</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">,</span> <span class="special">-</span><span class="number">2.0</span><span class="special">);</span>
<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"1.234e05"</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">,</span> <span class="number">1234.0e2</span><span class="special">);</span>
<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"1.234e-06"</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">,</span> <span class="number">0.000001234</span><span class="special">);</span>
</pre>
<p>
</p>
<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 © 2001-2010 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>
</div></td>
</tr></table>
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