| .. Sequences/Views//empty_sequence |
| |
| empty_sequence |
| ============== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| struct empty_sequence |
| { |
| // |unspecified| |
| // |...| |
| }; |
| |
| |
| Description |
| ----------- |
| |
| Represents a sequence containing no elements. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/empty_sequence.hpp> |
| |
| |
| Expression semantics |
| -------------------- |
| |
| |Semantics disclaimer...| |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 |
| ------- |
| |
| .. parsed-literal:: |
| |
| 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 ); |
| |
| |
| See also |
| -------- |
| |
| |Sequences|, |Views|, |vector|, |list|, |single_view| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
