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BOOST_MPL_ASSERT_NOT
Synopsis
#define BOOST_MPL_ASSERT_NOT( pred ) \ unspecified token sequence \ /**/
Description
Generates a compilation error when predicate holds true.
Header
#include <boost/mpl/assert.hpp>
Parameters
| Parameter | Requirement | Description |
|---|---|---|
| pred | Boolean nullary Metafunction | A predicate to be asserted to be false. |
Expression semantics
For any boolean nullary Metafunction pred:
BOOST_MPL_ASSERT_NOT(( pred ));
| Return type: | None. |
|---|---|
| Semantics: | Generates a compilation error if pred::type::value != false, otherwise has no effect. Note that double parentheses are required even if no commas appear in the condition. When possible within the compiler's diagnostic capabilities, the error message will include the predicate's full type name, and have a general form of: ... ************boost::mpl::not_< pred >::************ ... |
Example
template< typename T, typename U > struct my
{
// ...
BOOST_MPL_ASSERT_NOT(( is_same< T,U > ));
};
my<void,void> test;
// In instantiation of `my<void, void>':
// instantiated from here
// conversion from `
// mpl_::failed************boost::mpl::not_<boost::is_same<void, void>
// >::************' to non-scalar type `mpl_::assert<false>' requested