File: next_prior.hpp

package info (click to toggle)
boost1.62 1.62.0+dfsg-10
  • links: PTS, VCS
  • area: main
  • in suites: sid
  • size: 687,152 kB
  • sloc: cpp: 2,613,639; xml: 972,558; ansic: 53,674; python: 32,448; sh: 9,305; asm: 3,071; cs: 2,121; makefile: 967; perl: 859; yacc: 472; php: 132; ruby: 94; f90: 55; sql: 13; csh: 6
file content (165 lines) | stat: -rw-r--r-- 4,135 bytes parent folder | download | duplicates (15)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
//  Boost next_prior.hpp header file  ---------------------------------------//

//  (C) Copyright Dave Abrahams and Daniel Walker 1999-2003. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//  See http://www.boost.org/libs/utility for documentation.

//  Revision History
//  13 Dec 2003  Added next(x, n) and prior(x, n) (Daniel Walker)

#ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED
#define BOOST_NEXT_PRIOR_HPP_INCLUDED

#include <iterator>
#if defined(_MSC_VER) && _MSC_VER <= 1310
#include <boost/mpl/and.hpp>
#include <boost/type_traits/is_integral.hpp>
#endif
#include <boost/type_traits/is_unsigned.hpp>
#include <boost/type_traits/integral_promotion.hpp>
#include <boost/type_traits/make_signed.hpp>
#include <boost/type_traits/has_plus.hpp>
#include <boost/type_traits/has_plus_assign.hpp>
#include <boost/type_traits/has_minus.hpp>
#include <boost/type_traits/has_minus_assign.hpp>

namespace boost {

//  Helper functions for classes like bidirectional iterators not supporting
//  operator+ and operator-
//
//  Usage:
//    const std::list<T>::iterator p = get_some_iterator();
//    const std::list<T>::iterator prev = boost::prior(p);
//    const std::list<T>::iterator next = boost::next(prev, 2);

//  Contributed by Dave Abrahams

namespace next_prior_detail {

template< typename T, typename Distance, bool HasPlus = has_plus< T, Distance >::value >
struct next_impl2
{
    static T call(T x, Distance n)
    {
        std::advance(x, n);
        return x;
    }
};

template< typename T, typename Distance >
struct next_impl2< T, Distance, true >
{
    static T call(T x, Distance n)
    {
        return x + n;
    }
};


template< typename T, typename Distance, bool HasPlusAssign = has_plus_assign< T, Distance >::value >
struct next_impl1 :
    public next_impl2< T, Distance >
{
};

template< typename T, typename Distance >
struct next_impl1< T, Distance, true >
{
    static T call(T x, Distance n)
    {
        x += n;
        return x;
    }
};


template<
    typename T,
    typename Distance,
    typename PromotedDistance = typename integral_promotion< Distance >::type,
#if !defined(_MSC_VER) || _MSC_VER > 1310
    bool IsUInt = is_unsigned< PromotedDistance >::value
#else
    // MSVC 7.1 has problems with applying is_unsigned to non-integral types
    bool IsUInt = mpl::and_< is_integral< PromotedDistance >, is_unsigned< PromotedDistance > >::value
#endif
>
struct prior_impl3
{
    static T call(T x, Distance n)
    {
        std::advance(x, -n);
        return x;
    }
};

template< typename T, typename Distance, typename PromotedDistance >
struct prior_impl3< T, Distance, PromotedDistance, true >
{
    static T call(T x, Distance n)
    {
        typedef typename make_signed< PromotedDistance >::type signed_distance;
        std::advance(x, -static_cast< signed_distance >(static_cast< PromotedDistance >(n)));
        return x;
    }
};


template< typename T, typename Distance, bool HasMinus = has_minus< T, Distance >::value >
struct prior_impl2 :
    public prior_impl3< T, Distance >
{
};

template< typename T, typename Distance >
struct prior_impl2< T, Distance, true >
{
    static T call(T x, Distance n)
    {
        return x - n;
    }
};


template< typename T, typename Distance, bool HasMinusAssign = has_minus_assign< T, Distance >::value >
struct prior_impl1 :
    public prior_impl2< T, Distance >
{
};

template< typename T, typename Distance >
struct prior_impl1< T, Distance, true >
{
    static T call(T x, Distance n)
    {
        x -= n;
        return x;
    }
};

} // namespace next_prior_detail

template <class T>
inline T next(T x) { return ++x; }

template <class T, class Distance>
inline T next(T x, Distance n)
{
    return next_prior_detail::next_impl1< T, Distance >::call(x, n);
}

template <class T>
inline T prior(T x) { return --x; }

template <class T, class Distance>
inline T prior(T x, Distance n)
{
    return next_prior_detail::prior_impl1< T, Distance >::call(x, n);
}

} // namespace boost

#endif  // BOOST_NEXT_PRIOR_HPP_INCLUDED