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| <title>The MPL Reference Manual: BOOST_MPL_ASSERT_MSG</title> |
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| <div class="section" id="boost-mpl-assert-msg"> |
| <h1><a class="toc-backref" href="./asserts.html#id1589">BOOST_MPL_ASSERT_MSG</a></h1> |
| <div class="section" id="id1294"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| #define <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( condition, message, types ) \ |
| <em>unspecified token sequence</em> \ |
| /**/ |
| </pre> |
| </div> |
| <div class="section" id="id1295"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Generates a compilation error with an embedded custom message when the condition |
| doesn't hold.</p> |
| </div> |
| <div class="section" id="id1296"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/assert.hpp" class="header">boost/mpl/assert.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id1297"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
| <table border="1" class="docutils table"> |
| <colgroup> |
| <col width="15%" /> |
| <col width="36%" /> |
| <col width="48%" /> |
| </colgroup> |
| <thead valign="bottom"> |
| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">condition</span></tt></td> |
| <td>An integral constant expression</td> |
| <td>A condition to be asserted.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">message</span></tt></td> |
| <td>A legal identifier token</td> |
| <td>A custom message in a form of a legal C++ |
| identifier token.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">types</span></tt></td> |
| <td>A legal function parameter list</td> |
| <td>A parenthized list of types to be displayed |
| in the error message.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1298"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <p>For any integral constant expression <tt class="literal"><span class="pre">expr</span></tt>, legal C++ identifier <tt class="literal"><span class="pre">message</span></tt>, and |
| arbitrary types <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt>:</p> |
| <pre class="literal-block"> |
| <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( expr, message, (t1, t2,... tn) ); |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> are non-<tt class="literal"><span class="pre">void</span></tt>.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Generates a compilation error if <tt class="literal"><span class="pre">expr</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise |
| has no effect.</p> |
| <p>When possible within the compiler's diagnostic capabilities, |
| the error message will include the <tt class="literal"><span class="pre">message</span></tt> identifier and the parenthized |
| list of <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> types, and have a general form of:</p> |
| <pre class="last literal-block"> |
| <em>...</em> ************( <em>...</em>::message )************)(t1, t2,... tn) <em>...</em> |
| </pre> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| <pre class="literal-block"> |
| <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( expr, message, (types<t1, t2,... tn>) ); |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first">None.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Generates a compilation error if <tt class="literal"><span class="pre">expr</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise |
| has no effect.</p> |
| <p>When possible within the compiler's diagnostics capabilities, |
| the error message will include the <tt class="literal"><span class="pre">message</span></tt> identifier and the list of |
| <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> types, and have a general form of:</p> |
| <pre class="last literal-block"> |
| <em>...</em> ************( <em>...</em>::message )************)(types<t1, t2,... tn>) <em>...</em> |
| </pre> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id1299"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| template< typename T > struct my |
| { |
| // ... |
| <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( |
| is_integral<T>::value |
| , NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED |
| , (T) |
| ); |
| }; |
| |
| my<void*> test; |
| |
| // In instantiation of `my<void*>': |
| // instantiated from here |
| // conversion from ` |
| // mpl_::failed************(my<void*>:: |
| // NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED::************)(void*) |
| // ' to non-scalar type `mpl_::assert<false>' requested |
| </pre> |
| </div> |
| <div class="section" id="id1300"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <p><a class="reference internal" href="./asserts.html">Asserts</a>, <a class="reference internal" href="./assert.html">BOOST_MPL_ASSERT</a>, <a class="reference internal" href="./assert-not.html">BOOST_MPL_ASSERT_NOT</a>, <a class="reference internal" href="./assert-relation.html">BOOST_MPL_ASSERT_RELATION</a></p> |
| <!-- Macros/Asserts//BOOST_MPL_ASSERT_NOT --> |
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