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1 |
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2 #ifndef BOOST_MPL_VOID_HPP_INCLUDED |
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3 #define BOOST_MPL_VOID_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 // $Id: void.hpp 49267 2008-10-11 06:19:02Z agurtovoy $ |
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14 // $Date: 2008-10-11 02:19:02 -0400 (Sat, 11 Oct 2008) $ |
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15 // $Revision: 49267 $ |
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16 |
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17 #include <boost/mpl/void_fwd.hpp> |
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18 #include <boost/mpl/bool.hpp> |
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19 #include <boost/mpl/aux_/na_spec.hpp> |
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20 #include <boost/mpl/aux_/config/msvc.hpp> |
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21 #include <boost/mpl/aux_/config/workaround.hpp> |
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22 |
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23 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_OPEN |
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24 |
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25 // [JDG Feb-4-2003] made void_ a complete type to allow it to be |
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26 // instantiated so that it can be passed in as an object that can be |
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27 // used to select an overloaded function. Possible use includes signaling |
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28 // a zero arity functor evaluation call. |
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29 struct void_ { typedef void_ type; }; |
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30 |
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31 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_CLOSE |
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32 |
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33 namespace boost { namespace mpl { |
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34 |
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35 template< typename T > |
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36 struct is_void_ |
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37 : false_ |
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38 { |
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39 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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40 using false_::value; |
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41 #endif |
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42 }; |
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43 |
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44 template<> |
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45 struct is_void_<void_> |
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46 : true_ |
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47 { |
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48 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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49 using true_::value; |
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50 #endif |
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51 }; |
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52 |
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53 template< typename T > |
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54 struct is_not_void_ |
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55 : true_ |
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56 { |
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57 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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58 using true_::value; |
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59 #endif |
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60 }; |
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61 |
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62 template<> |
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63 struct is_not_void_<void_> |
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64 : false_ |
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65 { |
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66 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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67 using false_::value; |
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68 #endif |
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69 }; |
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70 |
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71 BOOST_MPL_AUX_NA_SPEC(1, is_void_) |
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72 BOOST_MPL_AUX_NA_SPEC(1, is_not_void_) |
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73 |
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74 }} |
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75 |
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76 #endif // BOOST_MPL_VOID_HPP_INCLUDED |