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1 | // Boost next_prior.hpp header file ---------------------------------------// |
2 | ||
3 | // (C) Copyright Dave Abrahams and Daniel Walker 1999-2003. Distributed under the Boost | |
4 | // Software License, Version 1.0. (See accompanying file | |
5 | // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
7 | // See http://www.boost.org/libs/utility for documentation. | |
8 | ||
9 | // Revision History | |
10 | // 13 Dec 2003 Added next(x, n) and prior(x, n) (Daniel Walker) | |
11 | ||
12 | #ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED | |
13 | #define BOOST_NEXT_PRIOR_HPP_INCLUDED | |
14 | ||
15 | #include <iterator> | |
16 | #if defined(_MSC_VER) && _MSC_VER <= 1310 | |
17 | #include <boost/mpl/and.hpp> | |
18 | #include <boost/type_traits/is_integral.hpp> | |
19 | #endif | |
20 | #include <boost/type_traits/is_unsigned.hpp> | |
21 | #include <boost/type_traits/integral_promotion.hpp> | |
22 | #include <boost/type_traits/make_signed.hpp> | |
23 | #include <boost/type_traits/has_plus.hpp> | |
24 | #include <boost/type_traits/has_plus_assign.hpp> | |
25 | #include <boost/type_traits/has_minus.hpp> | |
26 | #include <boost/type_traits/has_minus_assign.hpp> | |
27 | ||
28 | namespace boost { | |
29 | ||
30 | // Helper functions for classes like bidirectional iterators not supporting | |
31 | // operator+ and operator- | |
32 | // | |
33 | // Usage: | |
34 | // const std::list<T>::iterator p = get_some_iterator(); | |
35 | // const std::list<T>::iterator prev = boost::prior(p); | |
36 | // const std::list<T>::iterator next = boost::next(prev, 2); | |
37 | ||
38 | // Contributed by Dave Abrahams | |
39 | ||
40 | namespace next_prior_detail { | |
41 | ||
42 | template< typename T, typename Distance, bool HasPlus = has_plus< T, Distance >::value > | |
43 | struct next_impl2 | |
44 | { | |
45 | static T call(T x, Distance n) | |
46 | { | |
47 | std::advance(x, n); | |
48 | return x; | |
49 | } | |
50 | }; | |
51 | ||
52 | template< typename T, typename Distance > | |
53 | struct next_impl2< T, Distance, true > | |
54 | { | |
55 | static T call(T x, Distance n) | |
56 | { | |
57 | return x + n; | |
58 | } | |
59 | }; | |
60 | ||
61 | ||
62 | template< typename T, typename Distance, bool HasPlusAssign = has_plus_assign< T, Distance >::value > | |
63 | struct next_impl1 : | |
64 | public next_impl2< T, Distance > | |
65 | { | |
66 | }; | |
67 | ||
68 | template< typename T, typename Distance > | |
69 | struct next_impl1< T, Distance, true > | |
70 | { | |
71 | static T call(T x, Distance n) | |
72 | { | |
73 | x += n; | |
74 | return x; | |
75 | } | |
76 | }; | |
77 | ||
78 | ||
79 | template< | |
80 | typename T, | |
81 | typename Distance, | |
82 | typename PromotedDistance = typename integral_promotion< Distance >::type, | |
83 | #if !defined(_MSC_VER) || _MSC_VER > 1310 | |
84 | bool IsUInt = is_unsigned< PromotedDistance >::value | |
85 | #else | |
86 | // MSVC 7.1 has problems with applying is_unsigned to non-integral types | |
87 | bool IsUInt = mpl::and_< is_integral< PromotedDistance >, is_unsigned< PromotedDistance > >::value | |
88 | #endif | |
89 | > | |
90 | struct prior_impl3 | |
91 | { | |
92 | static T call(T x, Distance n) | |
93 | { | |
94 | std::advance(x, -n); | |
95 | return x; | |
96 | } | |
97 | }; | |
98 | ||
99 | template< typename T, typename Distance, typename PromotedDistance > | |
100 | struct prior_impl3< T, Distance, PromotedDistance, true > | |
101 | { | |
102 | static T call(T x, Distance n) | |
103 | { | |
104 | typedef typename make_signed< PromotedDistance >::type signed_distance; | |
105 | std::advance(x, -static_cast< signed_distance >(static_cast< PromotedDistance >(n))); | |
106 | return x; | |
107 | } | |
108 | }; | |
109 | ||
110 | ||
111 | template< typename T, typename Distance, bool HasMinus = has_minus< T, Distance >::value > | |
112 | struct prior_impl2 : | |
113 | public prior_impl3< T, Distance > | |
114 | { | |
115 | }; | |
116 | ||
117 | template< typename T, typename Distance > | |
118 | struct prior_impl2< T, Distance, true > | |
119 | { | |
120 | static T call(T x, Distance n) | |
121 | { | |
122 | return x - n; | |
123 | } | |
124 | }; | |
125 | ||
126 | ||
127 | template< typename T, typename Distance, bool HasMinusAssign = has_minus_assign< T, Distance >::value > | |
128 | struct prior_impl1 : | |
129 | public prior_impl2< T, Distance > | |
130 | { | |
131 | }; | |
132 | ||
133 | template< typename T, typename Distance > | |
134 | struct prior_impl1< T, Distance, true > | |
135 | { | |
136 | static T call(T x, Distance n) | |
137 | { | |
138 | x -= n; | |
139 | return x; | |
140 | } | |
141 | }; | |
142 | ||
143 | } // namespace next_prior_detail | |
144 | ||
145 | template <class T> | |
146 | inline T next(T x) { return ++x; } | |
147 | ||
148 | template <class T, class Distance> | |
149 | inline T next(T x, Distance n) | |
150 | { | |
151 | return next_prior_detail::next_impl1< T, Distance >::call(x, n); | |
152 | } | |
153 | ||
154 | template <class T> | |
155 | inline T prior(T x) { return --x; } | |
156 | ||
157 | template <class T, class Distance> | |
158 | inline T prior(T x, Distance n) | |
159 | { | |
160 | return next_prior_detail::prior_impl1< T, Distance >::call(x, n); | |
161 | } | |
162 | ||
163 | } // namespace boost | |
164 | ||
165 | #endif // BOOST_NEXT_PRIOR_HPP_INCLUDED |