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    <p>With macro, you can write a beautiful solution for problem such as this:</p> <ul> <li>Define an enum such that its value can be converted into its string representation and vice-versa.</li> </ul> <p>Suppose, you want to define an enum called <code>period</code> whose members are <code>one</code>, <code>five</code>, <code>ten</code>, <code>fifteen</code> and <code>thirty</code>. Then here is how you do it:</p> <ul> <li><p>First create a header file called <code>period_items.h</code> as:</p> <pre><code>//period_items.h //Here goes the items of the enum //it is not a definition in itself! E(one) E(five) E(ten) E(fifteen) E(thirty) </code></pre></li> <li><p>then create another header file called <code>period.h</code> as:</p> <pre><code>//period.h #include &lt;string&gt; //HERE goes the enum definition! enum period { #define E(item) item, #include "period_items.h" //it dumps the enum items in here! #undef E period_end }; period to_period(std::string const &amp; name) { #define E(item) if(name == #item) return item; #include "period_items.h" #undef E return period_end; } </code></pre></li> </ul> <p>Now you can simply include <code>period.h</code> and use <code>to_period</code> function. :-)</p> <p>You could also add this function to <code>period.h</code> as:</p> <pre><code>std::string to_string(period value) { #define E(item) if(value == item) return #item; #include "period_items.h" #undef E return "&lt;error&gt;"; } </code></pre> <p>Now, you could write this:</p> <pre><code>#include "period.h" period v = to_period("fifteen"); //string to period std::string s = to_string(v); //period to string </code></pre> <p><strong>Why this solution is beautiful?</strong></p> <p>Because now if you want to add few more members to the enum, all you have to do is to add them to <code>period_items.h</code> as:</p> <pre><code> //period_items.h //Here goes the items of the enum //it is not a definition in itself! E(one) E(five) E(ten) E(fifteen) E(thirty) E(fifty) //added item! E(hundred) //added item! E(thousand) //added item! </code></pre> <p>And you're done. <code>to_string</code> and <code>to_period</code> will work just fine, without any modification!</p> <p>--</p> <p>I took this solution from my solution to another problem, posted here:</p> <ul> <li><a href="https://stackoverflow.com/a/10887421/415784">converting from enum to int</a></li> </ul>
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    1. POWhen could macro make code more beautiful than function does?
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    1. USNawaz
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    1. COtalking about code obfuscation... I don't find it beautiful
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      1. USBЈовић
    2. COThis is a kludge. Kludges are usually clever but ugly, and this cannot be counted as an exception.
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      1. USakappa
    3. COI would not include a different header, but rather use a macro that takes a different macro as argument: `#define APPLY( MACRO ) MACRO(one) MACRO(two)` and then call it `enum X { #define ENUM_ITEM(x) x,` APPLY( ENUM_ITEM ) #undef ENUM_ITEM };`. This is more useful when there are concrete discrete values for the enum, or other mapped information, as you can have the `APPLY` macro pass multiple arguments. Say that you have a message protocol that sends `field_id`, `field_content`, and a given list of fields. You can have `APPLY` define the mapping: `#define APPLY( M ) M(my_field,value,type)`...
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      1. USDavid Rodríguez - dribeas
 

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