yangzuhao
73 lines
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73 lines
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_convert.other_conversions"></a><a class="link" href="other_conversions.html" title="Beyond Basic Conversions">Beyond Basic Conversions</a>
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</h2></div></div></div>
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<p>
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An interesting (and yet to be fully explored) property of the described design
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is that <span class="emphasis"><em>Boost.Convert</em></span> is not limited to string-to-type
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and type-to-string conversions. The <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">convert</span><span class="special">()</span></code> interface is type-agnostic and the plugged-in
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converter ultimately dictates what type transformations are available. Consequently,
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a wide range of conversion/transformation-related tasks can be addressed and
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<span class="emphasis"><em>deployed uniformly</em></span> by plugging-in special-purpose converters.
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</p>
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<p>
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As an experiment, the code below (taken from <span class="emphasis"><em>test/encryption.cpp</em></span>)
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does not do type conversion. Instead, it applies a string transformation:
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</p>
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<pre class="programlisting"><span class="identifier">string</span> <span class="identifier">encrypted</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">convert</span><span class="special"><</span><span class="identifier">string</span><span class="special">>(</span><span class="string">"ABC"</span><span class="special">,</span> <span class="identifier">my_cypher</span><span class="special">).</span><span class="identifier">value</span><span class="special">();</span>
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<span class="identifier">string</span> <span class="identifier">decrypted</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">convert</span><span class="special"><</span><span class="identifier">string</span><span class="special">>(</span><span class="identifier">encrypted</span><span class="special">,</span> <span class="identifier">my_cypher</span><span class="special">).</span><span class="identifier">value</span><span class="special">();</span>
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<span class="identifier">BOOST_ASSERT</span><span class="special">(</span><span class="identifier">encrypted</span> <span class="special">==</span> <span class="string">"123"</span><span class="special">);</span>
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<span class="identifier">BOOST_ASSERT</span><span class="special">(</span><span class="identifier">decrypted</span> <span class="special">==</span> <span class="string">"ABC"</span><span class="special">);</span>
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</pre>
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<p>
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The original "ABC" string is "encrypted" as "123"
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first and then "123" is "decrypted" back to its original
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"ABC" form.
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</p>
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<p>
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Similarly, I personally do not immediately see as objectionable string-transformations
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like:
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</p>
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<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">u8string</span> <span class="identifier">utf8</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">convert</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">u8string</span><span class="special">>(</span><span class="identifier">utf32_str</span><span class="special">,</span> <span class="identifier">cnv</span><span class="special">);</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">u8string</span> <span class="identifier">utf8</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">convert</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">u8string</span><span class="special">>(</span><span class="identifier">mbcs_str</span><span class="special">,</span> <span class="identifier">cnv</span><span class="special">);</span>
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</pre>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2009-2016 Vladimir Batov<p>
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Distributed under the Boost Software License, Version 1.0. See copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>.
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