1
2 // Copyright (C) 2009-2012 Lorenzo Caminiti
3 // Distributed under the Boost Software License, Version 1.0
4 // (see accompanying file LICENSE_1_0.txt or a copy at
5 // http://www.boost.org/LICENSE_1_0.txt)
6 // Home at http://www.boost.org/libs/local_function
7
8 #include "scope_exit.hpp"
9 #include <boost/foreach.hpp>
10 #include <boost/typeof/typeof.hpp>
11 #include <boost/typeof/std/vector.hpp>
12 #include BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP()
13 #include <boost/detail/lightweight_test.hpp>
14 #include <vector>
15 #include <iostream>
16 #include <sstream>
17
18 class person {
19 friend class world;
20 public:
21 typedef unsigned int id_t;
22 typedef unsigned int evolution_t;
23
person(void)24 person(void): id_(0), evolution_(0) {}
25
operator <<(std::ostream & o,person const & p)26 friend std::ostream& operator<<(std::ostream& o, person const& p) {
27 return o << "person(" << p.id_ << ", " << p.evolution_ << ")";
28 }
29 private:
30 id_t id_;
31 evolution_t evolution_;
32 };
33 BOOST_TYPEOF_REGISTER_TYPE(person)
34
35 class world {
36 public:
37 typedef unsigned int id_t;
38
world(void)39 world(void): next_id_(1) {}
40
41 void add_person(person const& a_person);
42
operator <<(std::ostream & o,world const & w)43 friend std::ostream& operator<<(std::ostream& o, world const& w) {
44 o << "world(" << w.next_id_ << ", {";
45 BOOST_FOREACH(person const& p, w.persons_) {
46 o << " " << p << ", ";
47 }
48 return o << "})";
49 }
50 private:
51 id_t next_id_;
52 std::vector<person> persons_;
53 };
BOOST_TYPEOF_REGISTER_TYPE(world)54 BOOST_TYPEOF_REGISTER_TYPE(world)
55
56 void world::add_person(person const& a_person) {
57 persons_.push_back(a_person);
58
59 // This block must be no-throw.
60 //[scope_exit
61 person& p = persons_.back();
62 person::evolution_t checkpoint = p.evolution_;
63
64 SCOPE_EXIT(const bind checkpoint, const bind& p, bind this_) {
65 if (checkpoint == p.evolution_) this_->persons_.pop_back();
66 } SCOPE_EXIT_END
67 //]
68
69 // ...
70
71 checkpoint = ++p.evolution_;
72
73 // Assign new id to the person.
74 world::id_t const prev_id = p.id_;
75 p.id_ = next_id_++;
76 SCOPE_EXIT(const bind checkpoint, const bind prev_id, bind& p,
77 bind& next_id_) {
78 if (checkpoint == p.evolution_) {
79 next_id_ = p.id_;
80 p.id_ = prev_id;
81 }
82 } SCOPE_EXIT_END
83
84 // ...
85
86 checkpoint = ++p.evolution_;
87 }
88
main(void)89 int main(void) {
90 person adam, eva;
91 std::ostringstream oss;
92 oss << adam;
93 std::cout << oss.str() << std::endl;
94 BOOST_TEST(oss.str() == "person(0, 0)");
95
96 oss.str("");
97 oss << eva;
98 std::cout << oss.str() << std::endl;
99 BOOST_TEST(oss.str() == "person(0, 0)");
100
101 world w;
102 w.add_person(adam);
103 w.add_person(eva);
104 oss.str("");
105 oss << w;
106 std::cout << oss.str() << std::endl;
107 BOOST_TEST(oss.str() == "world(3, { person(1, 2), person(2, 2), })");
108 return boost::report_errors();
109 }
110
111