1 ///////////////////////////////////////////////////////////////////////////////
2 //  Copyright 2015 John Maddock. Distributed under the Boost
3 //  Software License, Version 1.0. (See accompanying file
4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5 
6 #ifndef BOOST_MP_IS_BACKEND_HPP
7 #define BOOST_MP_IS_BACKEND_HPP
8 
9 #include <boost/mpl/has_xxx.hpp>
10 #include <boost/type_traits/conditional.hpp>
11 #include <boost/type_traits/is_convertible.hpp>
12 #include <boost/multiprecision/detail/number_base.hpp>
13 
14 namespace boost{ namespace multiprecision{  namespace detail{
15 
16    BOOST_MPL_HAS_XXX_TRAIT_DEF(signed_types)
17    BOOST_MPL_HAS_XXX_TRAIT_DEF(unsigned_types)
18    BOOST_MPL_HAS_XXX_TRAIT_DEF(float_types)
19 
20    template <class T>
21    struct is_backend
22    {
23       static const bool value = has_signed_types<T>::value && has_unsigned_types<T>::value && has_float_types<T>::value;
24    };
25 
26    template <class Backend>
27    struct other_backend
28    {
29       typedef typename boost::conditional<
30          boost::is_same<number<Backend>, number<Backend, et_on> >::value,
31          number<Backend, et_off>, number<Backend, et_on> >::type type;
32    };
33 
34    template <class B, class V>
35    struct number_from_backend
36    {
37       typedef typename boost::conditional <
38          boost::is_convertible<V, number<B> >::value,
39          number<B>,
40          typename other_backend<B>::type > ::type type;
41    };
42 
43    template <bool b, class T, class U>
44    struct is_first_backend_imp{ static const bool value = false; };
45    template <class T, class U>
46    struct is_first_backend_imp<true, T, U>{ static const bool value = is_convertible<U, number<T, et_on> >::value || is_convertible<U, number<T, et_off> >::value; };
47 
48    template <class T, class U>
49    struct is_first_backend : is_first_backend_imp<is_backend<T>::value, T, U> {};
50 
51    template <bool b, class T, class U>
52    struct is_second_backend_imp{ static const bool value = false; };
53    template <class T, class U>
54    struct is_second_backend_imp<true, T, U>{ static const bool value = (is_convertible<T, number<U, et_on> >::value || is_convertible<T, number<U, et_off> >::value) && !is_first_backend<T, U>::value; };
55 
56    template <class T, class U>
57    struct is_second_backend : is_second_backend_imp<is_backend<U>::value, T, U> {};
58 
59 }
60 }
61 }
62 
63 #endif // BOOST_MP_IS_BACKEND_HPP
64