The MPL Reference Manual: not_

not_

template<
      typename F
    >
struct not_
{
    typedef unspecified type;
};

Returns the result of logical not (!) operation on its argument.

#include <boost/mpl/not.hpp>
#include <boost/mpl/logical.hpp>

Parameter	Requirement	Description
`F`	Nullary Metafunction	Operation's argument.

For arbitrary nullary Metafunction f:

typedef not_<f>::type r;

Return type:

Return type:	Integral Constant.
Semantics:	Equivalent to typedef bool_< (!f::type::value) > r;

Semantics:

Equivalent to

typedef bool_< (!f::type::value) > r;

typedef not_<f> r;

Return type:

Return type:	Integral Constant.
Semantics:	Equivalent to struct r : not_<f>::type {};

Semantics:

Equivalent to

struct r : not_<f>::type {};

BOOST_MPL_ASSERT_NOT(( not_< true_ > ));
BOOST_MPL_ASSERT(( not_< false_ > ));

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