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1 ///////////////////////////////////////////////////////////////////////////////
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2 // Copyright Vicente J. Botet Escriba 2009-2011
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3 // Copyright 2012 John Maddock. Distributed under the Boost
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4 // Software License, Version 1.0. (See accompanying file
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5 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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6
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7 #ifndef BOOST_MP_EXPLICIT_CONVERTIBLE_HPP
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8 #define BOOST_MP_EXPLICIT_CONVERTIBLE_HPP
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9
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10 #include <boost/type_traits/is_convertible.hpp>
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11 #include <boost/utility/declval.hpp>
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12
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13
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14 namespace boost{ namespace multiprecision{ namespace detail{
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15
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16 template <int N>
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17 struct dummy_size{};
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18
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19 template<typename S, typename T>
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20 struct has_generic_interconversion
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21 {
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22 typedef typename mpl::if_c<
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23 is_number<S>::value && is_number<T>::value,
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24 typename mpl::if_c<
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25 number_category<S>::value == number_kind_integer,
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26 typename mpl::if_c<
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27 number_category<T>::value == number_kind_integer
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28 || number_category<T>::value == number_kind_floating_point
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29 || number_category<T>::value == number_kind_rational
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30 || number_category<T>::value == number_kind_fixed_point,
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31 mpl::true_,
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32 mpl::false_
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33 >::type,
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34 typename mpl::if_c<
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35 number_category<S>::value == number_kind_rational,
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36 typename mpl::if_c<
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37 number_category<T>::value == number_kind_rational
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38 || number_category<T>::value == number_kind_rational,
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39 mpl::true_,
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40 mpl::false_
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41 >::type,
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42 typename mpl::if_c<
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43 number_category<T>::value == number_kind_floating_point,
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44 mpl::true_,
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45 mpl::false_
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46 >::type
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47 >::type
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48 >::type,
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49 mpl::false_
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50 >::type type;
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51 };
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52
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53 template<typename S, typename T>
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54 struct is_explicitly_convertible_imp
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55 {
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56 #ifndef BOOST_NO_SFINAE_EXPR
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57 template<typename S1, typename T1>
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58 static type_traits::yes_type selector(dummy_size<sizeof(static_cast<T1>(declval<S1>()))>*);
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59
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60 template<typename S1, typename T1>
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61 static type_traits::no_type selector(...);
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62
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63 static const bool value = sizeof(selector<S,T>(0)) == sizeof(type_traits::yes_type);
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64
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65 typedef boost::integral_constant<bool,value> type;
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66 #else
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67 typedef typename has_generic_interconversion<S, T>::type gen_type;
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68 typedef mpl::bool_<boost::is_convertible<S, T>::value || gen_type::value> type;
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69 #endif
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70 };
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71
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72 template<typename From, typename To>
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73 struct is_explicitly_convertible : public is_explicitly_convertible_imp<From, To>::type
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74 {
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75 };
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76
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77 }}} // namespaces
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78
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79 #endif
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80
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