2004-11-28 03:35:12 +00:00
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2004-11-28 03:35:12 +00:00
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< title > The MPL Reference Manual: BOOST_MPL_ASSERT_RELATION</ 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-relation.html" class = "navigation-link" > BOOST_MPL_ASSERT_RELATION</ a ></ td >
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< div class = "section" id = "assert-relation" >
< h1 >< a class = "toc-backref" href = "./asserts.html#id514" name = "assert-relation" > BOOST_MPL_ASSERT_RELATION</ a ></ h1 >
< div class = "section" id = "the-macros-asserts-assert-synopsis" >
< h3 >< a class = "subsection-title" href = "#synopsis" name = "synopsis" > Synopsis</ a ></ h3 >
< pre class = "literal-block" >
#define < a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( x, relation, y ) \
< em > unspecified token sequence</ em > \
/**/
</ pre >
</ div >
< div class = "section" id = "the-macros-asserts-assert-description" >
< h3 >< a class = "subsection-title" href = "#description" name = "description" > Description</ a ></ h3 >
< p > A specialized assertion macro for checking numerical conditions. Generates
a compilation error when the condition < tt class = "literal" >< span class = "pre" > (</ span > < span class = "pre" > x</ span > < span class = "pre" > relation</ span > < span class = "pre" > y</ span > < span class = "pre" > )</ span ></ tt >
doesn't hold.</ p >
</ div >
< div class = "section" id = "the-macros-asserts-assert-header" >
< 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 >
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< div class = "section" id = "the-macros-asserts-assert-parameters" >
< h3 >< a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters</ a ></ h3 >
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< thead valign = "bottom" >
< tr >< th > Parameter</ th >
< th > Requirement</ th >
< th > Description</ th >
</ tr >
</ thead >
< tbody valign = "top" >
< tr >< td >< tt class = "literal" >< span class = "pre" > x</ span ></ tt ></ td >
< td > An integral constant</ td >
< td > Left operand of the checked relation.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > y</ span ></ tt ></ td >
< td > An integral constant</ td >
< td > Right operand of the checked relation.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > relation</ span ></ tt ></ td >
< td > A C++ operator token</ td >
< td > An operator token for the relation being
checked.</ td >
</ tr >
</ tbody >
</ table >
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< div class = "section" id = "the-macros-asserts-assert-expression-semantics" >
< h3 >< a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics</ a ></ h3 >
< p > For any integral constants < tt class = "literal" >< span class = "pre" > x</ span ></ tt > , < tt class = "literal" >< span class = "pre" > y</ span ></ tt > and a legal C++ operator token < tt class = "literal" >< span class = "pre" > op</ span ></ tt > :</ p >
< pre class = "literal-block" >
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( x, op, y );
</ pre >
< table class = "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" > None.</ 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" > (</ span > < span class = "pre" > x</ span > < span class = "pre" > op</ span > < span class = "pre" > y</ span > < span class = "pre" > )</ 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 a name of the relation being checked,
the actual values of both operands, and have a general form of:</ p >
< pre class = "last literal-block" >
< em > ...</ em > ************< em > ...</ em > assert_relation< op, x, y> ::************) < em > ...</ em >
</ pre >
</ td >
</ tr >
</ tbody >
</ table >
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< div class = "section" id = "the-macros-asserts-assert-example" >
< 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-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( sizeof(T), < , sizeof(U) );
};
my< char[50],char[10]> test;
// In instantiation of `my< char[50], char[10]> ':
// instantiated from here
// conversion from `
// mpl_::failed************mpl_::assert_relation< < a href = "./less.html" class = "identifier" > less</ a > , 50, 10> ::************'
// to non-scalar type `mpl_::assert< false> ' requested
</ pre >
</ div >
< div class = "section" id = "the-macros-asserts-assert-see-also" >
< h3 >< a class = "subsection-title" href = "#see-also" name = "see-also" > See also</ a ></ h3 >
< p >< a class = "reference" href = "./asserts.html" > Asserts</ a > , < a class = "refentry reference" href = "./assert.html" >< tt class = "refentry literal" >< span class = "pre" > BOOST_MPL_ASSERT</ span ></ tt ></ a > , < a class = "refentry reference" href = "./assert-not.html" >< tt class = "refentry literal" >< span class = "pre" > BOOST_MPL_ASSERT_NOT</ span ></ tt ></ a > , < a class = "refentry reference" href = "./assert-msg.html" >< tt class = "refentry literal" >< span class = "pre" > BOOST_MPL_ASSERT_MSG</ span ></ tt ></ a ></ p >
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