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BOOST_MPL_ASSERT

Synopsis

#define BOOST_MPL_ASSERT( pred ) \
    unspecified token sequence \
/**/

Description

Generates a compilation error when the predicate pred holds false.

Header

#include <boost/mpl/assert.hpp>

Parameters

Parameter Requirement Description
pred Boolean nullary Metafunction A predicate to be asserted.

Expression semantics

For any boolean nullary Metafunction pred:

BOOST_MPL_ASSERT(( pred ));
Return type:

None.

Semantics:

Generates a compilation error if pred::type::value != true, 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:

... ************ pred::************ ...

Example

template< typename T, typename U > struct my
{
    // ...
    BOOST_MPL_ASSERT(( is_same< T,U > ));
};

my<void*,char*> test;

// In instantiation of `my<void, char*>':
//   instantiated from here
// conversion from `
//   mpl_::failed************boost::is_same<void, char*>::************' to
//   non-scalar type `mpl_::assert<false>' requested

See also

Asserts, BOOST_MPL_ASSERT_NOT, BOOST_MPL_ASSERT_MSG, BOOST_MPL_ASSERT_RELATION