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Bitset Constructors [C++ Reference]
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<h2><a name="bitset_constructors" id="bitset_constructors">Bitset Constructors</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <bitset></span>
bitset<span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span>
bitset<span class="br0">(</span> <span class="kw4">unsigned</span> <span class="kw4">long</span> val <span class="br0">)</span><span class="sy0">;</span>
explicit bitset<span class="br0">(</span> <span class="kw4">const</span> string<span class="sy0">&</span> str<span class="sy0">,</span> <span class="kw4">string</span><span class="sy0">::</span><span class="me2">size_type</span> pos <span class="sy0">=</span> 0<span class="sy0">,</span> <span class="kw4">string</span><span class="sy0">::</span><span class="me2">size_type</span> n <span class="sy0">=</span> <span class="kw4">string</span><span class="sy0">::</span><span class="me2">npos</span> <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
Bitsets can be constructed with default values, from the bits in an unsigned long, or from string.
</p>
<ul>
<li class="level1"><div class="li"> The default value of a bit is 0.</div>
</li>
<li class="level1"><div class="li"> When an unsigned long argument is supplied, each bit in the integer is used to initialize the corresponding bit in the bitset (if any).</div>
</li>
<li class="level1"><div class="li"> A string argument does the same, except that the character '0' gives the bitvalue 0, the character '1' gives the bitvalue 1, and other characters cause an invalid_argument exception to be thrown. Note that this constructor is explicit. So no implicit type conversion from const char* to string is provided.</div>
</li>
</ul>
<p>
When creating bitsets, the number given in the place of the template determines
how long the bitset is.
</p>
<p>
For example, the following code creates two bitsets and displays them:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co1">// create a bitset that is 8 bits long</span>
bitset<span class="sy0"><</span>8<span class="sy0">></span> bs<span class="sy0">;</span>
<span class="co1">// display that bitset</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> bs <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="co1">// create a bitset out of a number</span>
bitset<span class="sy0"><</span>8<span class="sy0">></span> bs2<span class="br0">(</span> 131 <span class="br0">)</span><span class="sy0">;</span>
<span class="co1">// display that bitset, too</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> bs2 <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="co1">// create a bitset out of a string</span>
bitset<span class="sy0"><</span>8<span class="sy0">></span> bs3<span class="br0">(</span><span class="kw4">string</span><span class="br0">(</span><span class="st0">"10000000"</span><span class="br0">)</span><span class="br0">)</span><span class="sy0">;</span>
<span class="co1">// display the integer value of that bitset</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> bs3.<span class="me1">to_ulong</span><span class="br0">(</span><span class="br0">)</span> <span class="sy0"><<</span> endl<span class="sy0">;</span></pre>
<p>
When run, this code displays the following output:
</p>
<pre class="c code c++" style="font-family:monospace;"> 00000000
<span class="nu0">10000011</span>
<span class="nu0">128</span></pre>
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