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1 |
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2 #ifndef BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED |
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3 #define BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED |
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4 |
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5 // Copyright Aleksey Gurtovoy 2001-2004 |
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6 // |
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7 // Distributed under the Boost Software License, Version 1.0. |
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8 // (See accompanying file LICENSE_1_0.txt or copy at |
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9 // http://www.boost.org/LICENSE_1_0.txt) |
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10 // |
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11 // See http://www.boost.org/libs/mpl for documentation. |
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12 |
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13 // $Source: /cvsroot/boost/boost/boost/mpl/is_placeholder.hpp,v $ |
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14 // $Date: 2004/09/07 08:51:31 $ |
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15 // $Revision: 1.6 $ |
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16 |
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17 #include <boost/mpl/arg_fwd.hpp> |
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18 #include <boost/mpl/bool.hpp> |
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19 #include <boost/mpl/aux_/yes_no.hpp> |
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20 #include <boost/mpl/aux_/type_wrapper.hpp> |
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21 #include <boost/mpl/aux_/nttp_decl.hpp> |
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22 #include <boost/mpl/aux_/config/ctps.hpp> |
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23 #include <boost/mpl/aux_/config/static_constant.hpp> |
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24 |
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25 namespace boost { namespace mpl { |
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26 |
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27 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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28 |
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29 template< typename T > |
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30 struct is_placeholder |
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31 : bool_<false> |
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32 { |
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33 }; |
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34 |
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35 template< BOOST_MPL_AUX_NTTP_DECL(int, N) > |
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36 struct is_placeholder< arg<N> > |
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37 : bool_<true> |
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38 { |
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39 }; |
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40 |
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41 #else |
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42 |
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43 namespace aux { |
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44 |
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45 aux::no_tag is_placeholder_helper(...); |
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46 |
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47 template< BOOST_MPL_AUX_NTTP_DECL(int, N) > |
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48 aux::yes_tag is_placeholder_helper(aux::type_wrapper< arg<N> >*); |
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49 |
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50 } // namespace aux |
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51 |
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52 template< typename T > |
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53 struct is_placeholder |
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54 { |
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55 static aux::type_wrapper<T>* get(); |
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56 BOOST_STATIC_CONSTANT(bool, value = |
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57 sizeof(aux::is_placeholder_helper(get())) == sizeof(aux::yes_tag) |
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58 ); |
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59 |
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60 typedef bool_<value> type; |
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61 }; |
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62 |
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63 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
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64 |
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65 }} |
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66 |
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67 #endif // BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED |