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enum [C++ Reference]
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<h2><a name="enum" id="enum">enum</a></h2>
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<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw2">enum</span> name <span class="br0">{</span>name<span class="sy0">-</span>list<span class="br0">}</span> var<span class="sy0">-</span>list<span class="sy0">;</span></pre>
<p>
The enum keyword is used to create an enumerated type named name that consists
of the elements in name-list. The var-list argument is optional, and can be
used to create instances of the type along with the declaration. For example,
the following code creates an enumerated type for colors:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw2">enum</span> ColorT <span class="br0">{</span>red<span class="sy0">,</span> orange<span class="sy0">,</span> yellow<span class="sy0">,</span> green<span class="sy0">,</span> blue<span class="sy0">,</span> indigo<span class="sy0">,</span> violet<span class="br0">}</span><span class="sy0">;</span>
...
<span class="me1">ColorT</span> c1 <span class="sy0">=</span> indigo<span class="sy0">;</span>
<span class="kw1">if</span><span class="br0">(</span> c1 <span class="sy0">==</span> indigo <span class="br0">)</span> <span class="br0">{</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">"c1 is indigo"</span> <span class="sy0"><<</span> endl<span class="sy0">;</span>
<span class="br0">}</span></pre>
<p>
In the above example, the effect of the enumeration is to introduce several new
constants named red, orange, yellow, etc. By default, these constants are
assigned consecutive integer values starting at zero. You can change the values
of those constants, as shown by the next example:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw2">enum</span> ColorT <span class="br0">{</span> red <span class="sy0">=</span> 10<span class="sy0">,</span> blue <span class="sy0">=</span> 15<span class="sy0">,</span> green <span class="br0">}</span><span class="sy0">;</span>
...
<span class="me1">ColorT</span> c <span class="sy0">=</span> green<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">"c is "</span> <span class="sy0"><<</span> c <span class="sy0"><<</span> endl<span class="sy0">;</span></pre>
<p>
When executed, the above code will display the following output:
</p>
<pre class="c code c++" style="font-family:monospace;"> c is <span class="nu0">16</span></pre>
<p>
Note that the above examples will only work with C++ compilers. If you're
working in regular C, you will need to specify the enum keyword whenever you
create an instance of an enumerated type:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw2">enum</span> ColorT <span class="br0">{</span> red <span class="sy0">=</span> 10<span class="sy0">,</span> blue <span class="sy0">=</span> 15<span class="sy0">,</span> green <span class="br0">}</span><span class="sy0">;</span>
...
<span class="kw2">enum</span> ColorT c <span class="sy0">=</span> green<span class="sy0">;</span> <span class="coMULTI">/* note the additional enum keyword */</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"c is %d<span class="es1">\n</span>"</span><span class="sy0">,</span> c <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
Alternatively, add a typedef to bring C and C++ on par:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw4">typedef</span> <span class="kw2">enum</span> ColorT <span class="br0">{</span> red <span class="sy0">=</span> 10<span class="sy0">,</span> blue <span class="sy0">=</span> 15<span class="sy0">,</span> green <span class="br0">}</span> ColorT<span class="sy0">;</span>
...
<span class="me1">ColorT</span> c <span class="sy0">=</span> green<span class="sy0">;</span> <span class="coMULTI">/* no more additional enum keyword */</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">(</span> <span class="st0">"c is %d<span class="es1">\n</span>"</span><span class="sy0">,</span> c <span class="br0">)</span><span class="sy0">;</span></pre>
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