empty_sequence

Synopsis

struct empty_sequence
{
    // unspecified
    // ...
};

Description

Represents a sequence containing no elements.

Header

#include <boost/mpl/empty_sequence.hpp>

Expression semantics

The semantics of an expression are defined only where they differ from, or are not defined in Random Access Sequence.

In the following table, s is an instance of empty_sequence.

Expression	Semantics
`empty_sequence`	An empty Random Access Sequence.
`size<s>::type`	`size<s>::value == 0`; see Random Access Sequence.

Example

typedef begin<empty_sequence>::type first;
typedef end<empty_sequence>::type last;

BOOST_MPL_ASSERT(( is_same<first,last> ));
BOOST_MPL_ASSERT_RELATION( size<empty_sequence>::value, ==, 0 );

typedef transform_view<
      empty_sequence
    , add_pointer<_>
    > empty_view;

BOOST_MPL_ASSERT_RELATION( size<empty_sequence>::value, ==, 0 );