summaryrefslogtreecommitdiff
path: root/boost/hana/detail/algorithm.hpp
blob: 1929847e7a88d083db8e90651885c0daea8bc2cf (plain)
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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
/*!
@file
Defines several `constexpr` algorithms.

@copyright Louis Dionne 2013-2017
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
 */

#ifndef BOOST_HANA_DETAIL_ALGORITHM_HPP
#define BOOST_HANA_DETAIL_ALGORITHM_HPP

#include <boost/hana/functional/placeholder.hpp>

#include <boost/hana/config.hpp>

#include <cstddef>
#include <utility>


BOOST_HANA_NAMESPACE_BEGIN namespace detail {
    // Do not call this swap, otherwise it can get picked up by ADL and conflict
    // with std::swap (see https://github.com/boostorg/hana/issues/297).
    template <typename T>
    constexpr void constexpr_swap(T& x, T& y) {
        auto tmp = x;
        x = y;
        y = std::move(tmp);
    }

    template <typename BidirIter>
    constexpr void reverse(BidirIter first, BidirIter last) {
        while (first != last) {
            if (first == --last)
                break;
            detail::constexpr_swap(*first, *last);
            ++first;
        }
    }

    template <typename BidirIter, typename BinaryPred>
    constexpr bool next_permutation(BidirIter first, BidirIter last,
                                    BinaryPred pred)
    {
        BidirIter i = last;
        if (first == last || first == --i)
            return false;
        while (true) {
            BidirIter ip1 = i;
            if (pred(*--i, *ip1)) {
                BidirIter j = last;
                while (!pred(*i, *--j))
                    ;
                detail::constexpr_swap(*i, *j);
                detail::reverse(ip1, last);
                return true;
            }
            if (i == first) {
                detail::reverse(first, last);
                return false;
            }
        }
    }

    template <typename BidirIter>
    constexpr bool next_permutation(BidirIter first, BidirIter last)
    { return detail::next_permutation(first, last, hana::_ < hana::_); }


    template <typename InputIter1, typename InputIter2, typename BinaryPred>
    constexpr bool lexicographical_compare(InputIter1 first1, InputIter1 last1,
                                           InputIter2 first2, InputIter2 last2,
                                           BinaryPred pred)
    {
        for (; first2 != last2; ++first1, ++first2) {
            if (first1 == last1 || pred(*first1, *first2))
                return true;
            else if (pred(*first2, *first1))
                return false;
        }
        return false;
    }

    template <typename InputIter1, typename InputIter2>
    constexpr bool lexicographical_compare(InputIter1 first1, InputIter1 last1,
                                           InputIter2 first2, InputIter2 last2)
    { return detail::lexicographical_compare(first1, last1, first2, last2, hana::_ < hana::_); }


    template <typename InputIter1, typename InputIter2, typename BinaryPred>
    constexpr bool equal(InputIter1 first1, InputIter1 last1,
                         InputIter2 first2, InputIter2 last2,
                         BinaryPred pred)
    {
        for (; first1 != last1 && first2 != last2; ++first1, ++first2)
            if (!pred(*first1, *first2))
                return false;
        return first1 == last1 && first2 == last2;
    }

    template <typename InputIter1, typename InputIter2>
    constexpr bool equal(InputIter1 first1, InputIter1 last1,
                         InputIter2 first2, InputIter2 last2)
    { return detail::equal(first1, last1, first2, last2, hana::_ == hana::_); }


    template <typename BidirIter, typename BinaryPred>
    constexpr void sort(BidirIter first, BidirIter last, BinaryPred pred) {
        if (first == last) return;

        BidirIter i = first;
        for (++i; i != last; ++i) {
            BidirIter j = i;
            auto t = *j;
            for (BidirIter k = i; k != first && pred(t,  *--k); --j)
                *j = *k;
            *j = t;
        }
    }

    template <typename BidirIter>
    constexpr void sort(BidirIter first, BidirIter last)
    { detail::sort(first, last, hana::_ < hana::_); }


    template <typename InputIter, typename T>
    constexpr InputIter find(InputIter first, InputIter last, T const& value) {
        for (; first != last; ++first)
            if (*first == value)
                return first;
        return last;
    }

    template <typename InputIter, typename UnaryPred>
    constexpr InputIter find_if(InputIter first, InputIter last, UnaryPred pred) {
        for (; first != last; ++first)
            if (pred(*first))
                return first;
        return last;
    }

    template <typename ForwardIter, typename T>
    constexpr void iota(ForwardIter first, ForwardIter last, T value) {
        while (first != last) {
            *first++ = value;
            ++value;
        }
    }

    template <typename InputIt, typename T>
    constexpr std::size_t
    count(InputIt first, InputIt last, T const& value) {
        std::size_t n = 0;
        for (; first != last; ++first)
            if (*first == value)
                ++n;
        return n;
    }

    template <typename InputIt, typename T, typename F>
    constexpr T accumulate(InputIt first, InputIt last, T init, F f) {
        for (; first != last; ++first)
            init = f(init, *first);
        return init;
    }

    template <typename InputIt, typename T>
    constexpr T accumulate(InputIt first, InputIt last, T init) {
        return detail::accumulate(first, last, init, hana::_ + hana::_);
    }

    template <typename ForwardIt>
    constexpr ForwardIt min_element(ForwardIt first, ForwardIt last) {
        if (first == last)
            return last;

        ForwardIt smallest = first;
        ++first;
        for (; first != last; ++first)
            if (*first < *smallest)
                smallest = first;
        return smallest;
    }
} BOOST_HANA_NAMESPACE_END

#endif // !BOOST_HANA_DETAIL_ALGORITHM_HPP