Boost C++ Libraries

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empty
Description

Returns the result type of empty.

Synopsis
template<typename Seq>
struct empty
{
    typedef unspecified type;
};

Table 1.25. Parameters

Parameter

Requirement

Description

Seq

A model of Forward Sequence

Argument sequence


Expression Semantics
result_of::empty<Seq>::type

Return type: An MPL Integral Constant

Semantics: Returns mpl::true_ if Seq has zero elements, mpl::false_ otherwise.

Header
#include <boost/fusion/sequence/intrinsic/empty.hpp>
#include <boost/fusion/include/empty.hpp>
Example
typedef vector<> empty_vec;
typedef vector<int,float,char> vec;

BOOST_MPL_ASSERT((result_of::empty<empty_vec>));
BOOST_MPL_ASSERT_NOT((result_of::empty<vec>));

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