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 1.21. 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.

/sequence/intrinsic/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>));