boost/mpl/advance.hpp

0001
0002 #ifndef BOOST_MPL_ADVANCE_HPP_INCLUDED
0003 #define BOOST_MPL_ADVANCE_HPP_INCLUDED
0004
0005 // Copyright Aleksey Gurtovoy 2000-2004
0006 //
0007 // Distributed under the Boost Software License, Version 1.0.
0008 // (See accompanying file LICENSE_1_0.txt or copy at
0009 // http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 // See http://www.boost.org/libs/mpl for documentation.
0012
0013 // $Id$
0014 // $Date$
0015 // $Revision$
0016
0017 #include <boost/mpl/advance_fwd.hpp>
0018 #include <boost/mpl/less.hpp>
0019 #include <boost/mpl/negate.hpp>
0020 #include <boost/mpl/long.hpp>
0021 #include <boost/mpl/if.hpp>
0022 #include <boost/mpl/tag.hpp>
0023 #include <boost/mpl/apply_wrap.hpp>
0024 #include <boost/mpl/aux_/advance_forward.hpp>
0025 #include <boost/mpl/aux_/advance_backward.hpp>
0026 #include <boost/mpl/aux_/value_wknd.hpp>
0027 #include <boost/mpl/aux_/na_spec.hpp>
0028 #include <boost/mpl/aux_/nttp_decl.hpp>
0029
0030 namespace boost { namespace mpl {
0031
0032 // default implementation for forward/bidirectional iterators
0033 template< typename Tag >
0034 struct advance_impl
0035 {
0036     template< typename Iterator, typename N > struct apply
0037     {
0038         typedef typename less< N,long_<0> >::type backward_;
0039         typedef typename if_< backward_, negate<N>, N >::type offset_;
0040
0041         typedef typename if_<
0042               backward_
0043             , aux::advance_backward< BOOST_MPL_AUX_VALUE_WKND(offset_)::value >
0044             , aux::advance_forward< BOOST_MPL_AUX_VALUE_WKND(offset_)::value >
0045             >::type f_;
0046
0047         typedef typename apply_wrap1<f_,Iterator>::type type;
0048     };
0049 };
0050
0051
0052 template<
0053       typename BOOST_MPL_AUX_NA_PARAM(Iterator)
0054     , typename BOOST_MPL_AUX_NA_PARAM(N)
0055     >
0056 struct advance
0057     : advance_impl< typename tag<Iterator>::type >
0058         ::template apply<Iterator,N>
0059 {
0060 };
0061
0062 template<
0063       typename Iterator
0064     , BOOST_MPL_AUX_NTTP_DECL(long, N)
0065     >
0066 struct advance_c
0067     : advance_impl< typename tag<Iterator>::type >
0068         ::template apply<Iterator,long_<N> >
0069 {
0070 };
0071
0072 BOOST_MPL_AUX_NA_SPEC(2, advance)
0073
0074 }}
0075
0076 #endif // BOOST_MPL_ADVANCE_HPP_INCLUDED