1 // Copyright (C) 2019 T. Zachary Laine
2 //
3 // Distributed under the Boost Software License, Version 1.0. (See
4 // accompanying file LICENSE_1_0.txt or copy at
5 // http://www.boost.org/LICENSE_1_0.txt)
6 #include <boost/stl_interfaces/iterator_interface.hpp>
7
8 #include <algorithm>
9 #include <array>
10 #include <iostream>
11
12 #include <cassert>
13
14
15 //[ node_defn
16 template<typename T>
17 struct node
18 {
19 T value_;
20 node * next_; // == nullptr in the tail node
21 };
22 //]
23
24 //[ node_iterator_class_head
25 template<typename T>
26 struct node_iterator
27 : boost::stl_interfaces::
28 iterator_interface<node_iterator<T>, std::forward_iterator_tag, T>
29 //]
30 {
31 //[ node_iterator_ctors
node_iteratornode_iterator32 constexpr node_iterator() noexcept : it_(nullptr) {}
node_iteratornode_iterator33 constexpr node_iterator(node<T> * it) noexcept : it_(it) {}
34 //]
35
36 //[ node_iterator_user_ops
operator *node_iterator37 constexpr T & operator*() const noexcept { return it_->value_; }
operator ++node_iterator38 constexpr node_iterator & operator++() noexcept
39 {
40 it_ = it_->next_;
41 return *this;
42 }
43 friend constexpr bool
operator ==(node_iterator lhs,node_iterator rhs)44 operator==(node_iterator lhs, node_iterator rhs) noexcept
45 {
46 return lhs.it_ == rhs.it_;
47 }
48 //]
49
50 //[ node_iterator_using_declaration
51 using base_type = boost::stl_interfaces::
52 iterator_interface<node_iterator<T>, std::forward_iterator_tag, T>;
53 using base_type::operator++;
54 //]
55
56 private:
57 node<T> * it_;
58 };
59
60 //[ node_iterator_concept_check Equivalent to
61 // static_assert(std::forward_iterator<node_iterator>, ""), or nothing in
62 // C++17 and earlier.
BOOST_STL_INTERFACES_STATIC_ASSERT_CONCEPT(node_iterator,std::forward_iterator)63 BOOST_STL_INTERFACES_STATIC_ASSERT_CONCEPT(node_iterator, std::forward_iterator)
64 //]
65
66
67 int main()
68 {
69 std::array<node<int>, 5> nodes;
70 std::generate(nodes.begin(), nodes.end(), [] {
71 static int i = 0;
72 return node<int>{i++};
73 });
74 std::adjacent_find(
75 nodes.begin(), nodes.end(), [](node<int> & a, node<int> & b) {
76 a.next_ = &b;
77 return false;
78 });
79 nodes.back().next_ = nullptr;
80
81 //[ node_iterator_usage
82 node_iterator<int> const first(&nodes[0]);
83 node_iterator<int> const last;
84 for (auto it = first; it != last; it++) {
85 std::cout << *it << " "; // Prints 0 1 2 3 4
86 }
87 std::cout << "\n";
88 //]
89 }
90