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POWhat are preprocessor macros good for?
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  1. POWhat are preprocessor macros good for?
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    copied!<p>After reading another question about the use of macros, I wondered: What <em>are</em> they good for?</p> <p>One thing I don't see replaced by any other language construct very soon is in diminishing the number of related words you need to type in the following:</p> <pre><code>void log_type( const bool value ) { std::cout &lt;&lt; "bool: " &lt;&lt; value; } void log_type( const int value ) { std::cout &lt;&lt; "int: " &lt;&lt; value; } ... void log_type( const char value ) { std::cout &lt;&lt; "char: " &lt;&lt; value; } void log_type( const double value ) { std::cout &lt;&lt; "int: " &lt;&lt; value; } void log_type( const float value ) { std::cout &lt;&lt; "float: " &lt;&lt; value; } </code></pre> <p>as opposed to</p> <pre><code>#define LOGFN( T ) void log_type( const T value ) { std::cout &lt;&lt; #T ## ": " &lt;&lt; value; } LOGFN( int ) LOGFN( bool ) ... LOGFN( char ) LOGFN( double ) LOGFN( float ) </code></pre> <p>Any other 'irreplaceables'?</p> <p>EDIT: trying to summarize the reasons-why encountered in the answers; since that's what I was interested in. Mainly because I have a feeling that most of them are due to us still programming in raw text files in, still, poorly supporting environments.</p> <ul> <li>flexibility of code-to-be compiled (e.g. <code>#ifdef DEBUG</code>, platform issues) (SadSido, Catalin, Goz)</li> <li>debug purposes (e.g. <code>__LINE__, __TIME__</code>); I also put 'stringifying' under this reason (SadSido, Jla3ep, Jason S)</li> <li>replacing e.g. PHP's <code>require</code> vs. <code>include</code> feature (<code>#pragma once</code>) (SadSido, Catalin)</li> <li>readability enhancement by replacing complicated code (e.g. <code>MESSAGEMAP</code>, <code>BOOST_FOREACH</code>) (SadSido, fnieto)</li> <li>DRY principle (Jason S)</li> <li>an inline replacement (Matthias Wandel, Robert S. Barnes)</li> <li>stringifying (Jason S)</li> </ul>
 

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