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    <p><code>enum class</code> is called a <em>scoped enumeration</em>. It prevents polluting the namespace where the enumeration appears with the names of the enumerators.</p> <p>In C++03, you could do effectively the same thing by putting the <code>enum</code> inside a dedicated <code>class</code>. Perhaps that's the source of the syntax, which is a bit confusing.</p> <p>Another difference is that the enumerators of such a type don't convert implicitly to <code>int</code> (<code>static_cast&lt;int&gt;</code> is required). This may be seldom <em>needed</em> but it makes it safe to overload a function taking an <code>int</code> argument with one taking <code>enum</code> type. You can be sure the <code>int</code> won't be called by accident. Or you can define pseudo-integral types with dedicated <code>operator</code> functions, and be sure that built-in operators won't interfere.</p> <p>It's a bit annoying that these two unrelated differences come in the same package, and that you can't get an <em>unscoped</em> enumeration with no implicit conversion, but generally both changes are Good Things and <code>enum class</code> is a good default practice in C++11.</p> <p><strong>EDIT:</strong> A scoped enumeration is defined like this:</p> <pre><code>enum class duck { huey, dewey, louie }; </code></pre> <p>and must be used with the scope resolution operator <code>::</code> like this:</p> <pre><code>duck culprit = duck::huey; // or "auto culprit" to avoid redundancy </code></pre> <p>Note that the <code>::</code> operator also works with C++03 unscoped enumerations, so the second line above would work even if the first was missing <code>class</code>.</p> <p>This might be excessive detail, but <code>class</code> does not go into the <em>elaborated-type-specifier</em> if forward declaring the enumerated type, as in</p> <pre><code>void quack( enum duck whom ); // not "enum class" </code></pre> <p>However, there is a construct new in C++11, the <em>opaque-enum-declaration</em>, which does include the <code>class</code> keyword and defines a complete type.</p> <pre><code>enum duck; // duck is declared as incomplete type enum class duck; // duck is now complete type; underlying type defaults to int </code></pre> <p>The keyword <code>struct</code> can be substituted for <code>class</code> with no semantic difference.</p>
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    1. POWhat's an enum class and why should I care?
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    1. COAh, finally what seems to be a good answer. Thank you, `+1` from me. Can you elaborate on the syntax? How do you define such a beast? I am sure I have seen it somewhere a few years ago, but I forgot.
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    2. CO@sbi not much to elaborate, you just add the `class` keyword to any `enum` definition and get these semantic changes.
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    3. COThanks, though, for still adding it. I feel like this answer is now a comprehensive explanation and I'll therefore accept it. (Although I won't promise to not to jump ship when something better comes along later. `:)` )
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