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numeric_limits [C++ Reference]
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<h2><a name="numeric_limits" id="numeric_limits">numeric_limits</a></h2>
<div class="level2">
<p>
This templated class provides various information about the built-in types.
</p>
<p>
Limits for numeric values are defined in the <limits> header. The templated values of numeric_limits provide system-dependent numerical representations of the C++ data types. Use the appropriate function given the data type as the template argument as shown in the table below. Note that numeric_limits can be overloaded for user-defined types as well.
</p>
<table class="inline">
<tr class="row0">
<th class="col0">Method or<br/>
constant</th><th class="col1">Return</th><th class="col2">Description</th>
</tr>
<tr class="row1">
<td class="col0">is_specialized</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row2">
<td class="col0">radix</td><td class="col1">int</td><td class="col2">base of exponent</td>
</tr>
<tr class="row3">
<td class="col0">digits</td><td class="col1">int</td><td class="col2">number of radix digits in mantissa</td>
</tr>
<tr class="row4">
<td class="col0">digits10</td><td class="col1">int</td><td class="col2">number of base 10 digits in mantissa</td>
</tr>
<tr class="row5">
<td class="col0">is_signed</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row6">
<td class="col0">is_integer</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row7">
<td class="col0">is_exact</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row8">
<td class="col0">min()</td><td class="col1"><type></td><td class="col2">smallest number that can be respresented (not the most negative)</td>
</tr>
<tr class="row9">
<td class="col0">max()</td><td class="col1"><type></td><td class="col2">largest number</td>
</tr>
<tr class="row10">
<td class="col0">epsilon()</td><td class="col1"><type></td><td class="col2">inherent representation error value, so that 1 + epsilon > 1 </td>
</tr>
<tr class="row11">
<td class="col0">round_error()</td><td class="col1"><type></td><td class="col2">maximum rounding adjustment possible</td>
</tr>
<tr class="row12">
<td class="col0">infinity()</td><td class="col1"><type></td><td class="col2"> </td>
</tr>
<tr class="row13">
<td class="col0">quiet_NaN()</td><td class="col1"><type></td><td class="col2">invalid number that does not signal floating point error</td>
</tr>
<tr class="row14">
<td class="col0">signaling_NaN()</td><td class="col1"><type></td><td class="col2">invalid number that signals floating point error</td>
</tr>
<tr class="row15">
<td class="col0">denorm_min()</td><td class="col1"><type></td><td class="col2"> </td>
</tr>
<tr class="row16">
<td class="col0">min_exponent</td><td class="col1">int</td><td class="col2"> </td>
</tr>
<tr class="row17">
<td class="col0">min_exponent10</td><td class="col1">int</td><td class="col2"> </td>
</tr>
<tr class="row18">
<td class="col0">max_exponent</td><td class="col1">int</td><td class="col2"> </td>
</tr>
<tr class="row19">
<td class="col0">max_exponent10</td><td class="col1">int</td><td class="col2"> </td>
</tr>
<tr class="row20">
<td class="col0">has_infinity</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row21">
<td class="col0">has_quiet_NaN</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row22">
<td class="col0">has_signaling_NaN</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row23">
<td class="col0">has_denorm</td><td class="col1"><type>_denorm_style</td><td class="col2"> </td>
</tr>
<tr class="row24">
<td class="col0">has_denorm_loss</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row25">
<td class="col0">is_iec559</td><td class="col1">bool</td><td class="col2">conforms to IEC-559</td>
</tr>
<tr class="row26">
<td class="col0">is_bounded</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row27">
<td class="col0">is_modulo</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row28">
<td class="col0">traps</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row29">
<td class="col0">tinyness_before</td><td class="col1">bool</td><td class="col2"> </td>
</tr>
<tr class="row30">
<td class="col0">round_style</td><td class="col1">float_round_style { round_to_nearest, … }</td><td class="col2"> </td>
</tr>
</table>
<p>
The most common usage is in bounds checking, to determine the minimum and maximum values a data type can hold. The following code prints out the minimum and maximum values for a short on the system it is run.
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <limits></span>
std<span class="sy0">::</span><a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"Maximum short value: "</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">numeric_limits</span><span class="sy0"><</span>short<span class="sy0">>::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">endl</span><span class="sy0">;</span>
std<span class="sy0">::</span><a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"Minimum short value: "</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">numeric_limits</span><span class="sy0"><</span>short<span class="sy0">>::</span><span class="me2">min</span><span class="br0">(</span><span class="br0">)</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">endl</span><span class="sy0">;</span></pre>
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