empty

| Home | Libraries | People | FAQ | More

##### 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>));