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| 26 | <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
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| 27 | <a name="any.reference"></a>Reference</h2></div></div></div> |
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| 28 | <div class="toc"><dl> |
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| 29 | <dt><span class="section"><a href="reference.html#any.ValueType"><span class="emphasis"><em>ValueType</em></span> requirements</a></span></dt> |
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| 30 | <dt><span class="section"><a href="reference.html#header.boost.any.hpp">Header <boost/any.hpp></a></span></dt> |
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| 31 | </dl></div> |
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| 32 | <div class="section" lang="en"> |
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| 33 | <div class="titlepage"><div><div><h3 class="title"> |
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| 34 | <a name="any.ValueType"></a><span class="emphasis"><em>ValueType</em></span> requirements</h3></div></div></div> |
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| 35 | <p>Values are strongly informational objects for which |
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| 36 | identity is not significant, i.e. the focus is principally on |
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| 37 | their state content and any behavior organized around |
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| 38 | that. Another distinguishing feature of values is their |
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| 39 | granularity: normally fine-grained objects representing simple |
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| 40 | concepts in the system such as quantities.</p> |
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| 41 | <p>As the emphasis of a value lies in its state not its |
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| 42 | identity, values can be copied and typically assigned one to |
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| 43 | another, requiring the explicit or implicit definition of a |
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| 44 | public copy constructor and public assignment operator. Values |
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| 45 | typically live within other scopes, i.e. within objects or |
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| 46 | blocks, rather than on the heap. Values are therefore normally |
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| 47 | passed around and manipulated directly as variables or through |
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| 48 | references, but not as pointers that emphasize identity and |
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| 49 | indirection.</p> |
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| 50 | <p>The specific requirements on value types to be used in an |
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| 51 | <code class="computeroutput"><a href="../boost/any.html" title="Class any">any</a></code> |
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| 52 | are:</p> |
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| 53 | <div class="itemizedlist"><ul type="disc" compact> |
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| 54 | <li>A <span class="emphasis"><em>ValueType</em></span> is |
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| 55 | <span class="emphasis"><em>CopyConstructible</em></span> [20.1.3].</li> |
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| 56 | <li>A <span class="emphasis"><em>ValueType</em></span> is |
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| 57 | optionally <span class="emphasis"><em>Assignable</em></span> [23.1]. The strong |
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| 58 | exception-safety guarantee is required for all forms of |
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| 59 | assignment.</li> |
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| 60 | <li>The destructor for a |
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| 61 | <span class="emphasis"><em>ValueType</em></span> upholds the no-throw |
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| 62 | exception-safety guarantee.</li> |
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| 63 | </ul></div> |
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| 64 | </div> |
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| 65 | <div class="section" lang="en"> |
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| 66 | <div class="titlepage"><div><div><h3 class="title"> |
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| 67 | <a name="header.boost.any.hpp"></a>Header <<a href="../../../boost/any.hpp" target="_top">boost/any.hpp</a>></h3></div></div></div> |
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| 68 | <pre class="synopsis"><span class="bold"><strong>namespace</strong></span> boost { |
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| 69 | <span class="bold"><strong>class</strong></span> <a href="../boost/bad_any_cast.html" title="Class bad_any_cast">bad_any_cast</a>; |
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| 70 | <span class="bold"><strong>class</strong></span> <a href="../boost/any.html" title="Class any">any</a>; |
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| 71 | <span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> T> <span class="type">T</span> <a href="../boost/any_cast.html" title="Function any_cast">any_cast</a>(<a href="../boost/any.html" title="Class any">any</a> &); |
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| 72 | <span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> T> <span class="type">T</span> <a href="../boost/any_cast.html" title="Function any_cast">any_cast</a>(<span class="bold"><strong>const</strong></span> <a href="../boost/any.html" title="Class any">any</a> &); |
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| 73 | <span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> ValueType> <span class="type"><span class="bold"><strong>const</strong></span> ValueType *</span> <a href="../boost/any_cast.html" title="Function any_cast">any_cast</a>(<span class="bold"><strong>const</strong></span> <a href="../boost/any.html" title="Class any">any</a> *); |
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| 74 | <span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> ValueType> <span class="type">ValueType *</span> <a href="../boost/any_cast.html" title="Function any_cast">any_cast</a>(<a href="../boost/any.html" title="Class any">any</a> *); |
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| 75 | }</pre> |
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| 76 | </div> |
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| 77 | </div> |
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| 78 | <table width="100%"><tr> |
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| 79 | <td align="left"></td> |
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| 80 | <td align="right"><small>Copyright © 2001 Kevlin Henney</small></td> |
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