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POSupport for const_string in std::ostream operator <<
 

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    <p>I'm currently using the very clever package <a href="http://conststring.sourceforge.net/" rel="nofollow"><code>boost::const_string</code></a> until <a href="http://libcxx.llvm.org/" rel="nofollow">http://libcxx.llvm.org/</a> is available pre-packaged on Ubuntu or GCC make its <code>__versa_string</code> (in header <code>ext/vstring.h</code>) its default string implementation. libcxx's <code>std::string</code> aswell as <code>__versa_string</code> uses _small-string optimization (SSO) by default. Default support for outputting to an <code>std::ostream</code> is lacking however. The code</p> <pre><code>#include &lt;iostream&gt; #include &lt;boost/const_string.hpp&gt; const_string&lt;char&gt; x; std::cout &lt;&lt; x &lt;&lt; endl; </code></pre> <p>does not work unless we force <code>x</code> into a c-string via <code>c_str()</code> which becomes</p> <pre><code>std::cout &lt;&lt; x.c_str() &lt;&lt; endl; </code></pre> <p>which compiles and works as expected. I added the following line to <code>const_string.hpp</code></p> <pre><code>template &lt;typename T&gt; inline std::ostream &amp; operator &lt;&lt; (std::ostream &amp; os, const boost::const_string&lt;T&gt; &amp; a) { return os.write(a.data(), a.size()); } </code></pre> <p>This should improve performance over <code>x.c_str()</code> because <code>size()</code> is already known and does not need to be calculated by searching for <code>NULL</code> as in <code>c_str()</code>. I works for me but I am uncertain whether it works all cases. Have I missed something?</p>
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    1. COThat depends on which behaviour you want for non-printable characters (especially `\0`), I guess. I think (!) the default behaviour for normal strings is to truncate after null chars. Your implementation probably won’t do that. By the way, +1 for making me aware of `boost::const_string`.
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      1. USKonrad Rudolph
    2. COI think this is a kind of trade-off. As far as I see, your code doesn't reflect manipulator settings like `std::setw`. If you don't use those manipulators for `const_string`, I think your code has its own use.
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      1. USIse Wisteria
 

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