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< title > The MPL Reference Manual: BOOST_MPL_ASSERT</ title >
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< td class = "header-group page-location" >< a href = "../refmanual.html" class = "navigation-link" > Front Page</ a > / < a href = "./macros.html" class = "navigation-link" > Macros</ a > / < a href = "./asserts.html" class = "navigation-link" > Asserts</ a > / < a href = "./assert.html" class = "navigation-link" > BOOST_MPL_ASSERT</ a ></ td >
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< div class = "section" id = "boost-mpl-assert" >
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< h1 >< a class = "toc-backref" href = "./asserts.html#id1588" > BOOST_MPL_ASSERT</ a ></ h1 >
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< div class = "section" id = "id1287" >
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< h3 >< a class = "subsection-title" href = "#synopsis" name = "synopsis" > Synopsis</ a ></ h3 >
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#define < a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > ( pred ) \
< em > unspecified token sequence</ em > \
/**/
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< div class = "section" id = "id1288" >
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< h3 >< a class = "subsection-title" href = "#description" name = "description" > Description</ a ></ h3 >
< p > Generates a compilation error when the predicate < tt class = "literal" >< span class = "pre" > pred</ span ></ tt > holds false.</ p >
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< div class = "section" id = "id1289" >
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< h3 >< a class = "subsection-title" href = "#header" name = "header" > Header</ a ></ h3 >
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#include < < a href = "../../../../boost/mpl/assert.hpp" class = "header" > boost/mpl/assert.hpp</ a > >
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< div class = "section" id = "id1290" >
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< h3 >< a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters</ a ></ h3 >
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< tr >< th class = "head" > Parameter</ th >
< th class = "head" > Requirement</ th >
< th class = "head" > Description</ th >
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</ tr >
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< tr >< td >< tt class = "literal" >< span class = "pre" > pred</ span ></ tt ></ td >
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< td > Boolean nullary < a class = "reference internal" href = "./metafunction.html" > Metafunction</ a ></ td >
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< td > A predicate to be asserted.</ td >
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< div class = "section" id = "id1291" >
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< h3 >< a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics</ a ></ h3 >
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< p > For any boolean nullary < a class = "reference internal" href = "./metafunction.html" > Metafunction</ a > < tt class = "literal" >< span class = "pre" > pred</ span ></ tt > :</ p >
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< pre class = "literal-block" >
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( pred ));
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< tr class = "field" >< th class = "field-name" > Return type:</ th >< td class = "field-body" >< p class = "first" > None.</ p >
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< 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" > pred::type::value</ span > < span class = "pre" > !=</ span > < span class = "pre" > true</ span ></ tt > , otherwise
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has no effect. Note that double parentheses are required even if no commas
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appear in the condition.</ p >
< p > When possible within the compiler's diagnostic capabilities,
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the error message will include the predicate's full type name, and have a
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general form of:</ p >
< pre class = "last literal-block" >
< em > ...</ em > ************ pred::************ < em > ...</ em >
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< div class = "section" id = "id1292" >
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< h3 >< a class = "subsection-title" href = "#example" name = "example" > Example</ a ></ h3 >
< pre class = "literal-block" >
template< typename T, typename U > struct my
{
// ...
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( is_same< T,U > ));
};
my< void*,char*> test;
// In instantiation of `my< void, char*> ':
// instantiated from here
// conversion from `
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// mpl_::failed************boost::is_same< void, char*> ::************' to
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// non-scalar type `mpl_::assert< false> ' requested
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< div class = "section" id = "id1293" >
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< h3 >< a class = "subsection-title" href = "#see-also" name = "see-also" > See also</ a ></ h3 >
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< p >< a class = "reference internal" href = "./asserts.html" > Asserts</ a > , < a class = "reference internal" href = "./assert-not.html" > BOOST_MPL_ASSERT_NOT</ a > , < a class = "reference internal" href = "./assert-msg.html" > BOOST_MPL_ASSERT_MSG</ a > , < a class = "reference internal" href = "./assert-relation.html" > BOOST_MPL_ASSERT_RELATION</ a ></ p >
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<!-- Macros/Asserts//BOOST_MPL_ASSERT_MSG -->
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< td >< div class = "copyright-footer" >< div class = "copyright" > Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</ div >
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