1
2 // Copyright (C) 2008-2018 Lorenzo Caminiti
3 // Distributed under the Boost Software License, Version 1.0 (see accompanying
4 // file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
5 // See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
6
7 #include <boost/contract.hpp>
8 #include <boost/optional.hpp>
9 #include <cassert>
10
11 //[named_override_pure_virtual_assert_false
12 template<typename T>
13 class generic_unary_pack {
14 public:
15 virtual void _1(T const& value, boost::contract::virtual_* v = 0) = 0;
16 virtual T _1(boost::contract::virtual_* v = 0) const = 0;
17 };
18
19 template<typename T>
_1(T const & value,boost::contract::virtual_ * v)20 void generic_unary_pack<T>::_1(T const& value, boost::contract::virtual_* v) {
21 boost::contract::check c = boost::contract::public_function(v, this)
22 .precondition([&] {
23 BOOST_CONTRACT_ASSERT(false); // Defer preconditions to overrides.
24 })
25 ;
26 assert(false);
27 }
28
29 /* ... */
30 //]
31
32 template<typename T>
_1(boost::contract::virtual_ * v) const33 T generic_unary_pack<T>::_1(boost::contract::virtual_* v) const {
34 boost::optional<T> result; // Do not assume T has default constructor.
35 boost::contract::check c = boost::contract::public_function(v, result, this)
36 .postcondition([&] (boost::optional<T const&> const& result) {
37 BOOST_CONTRACT_ASSERT(*result == _1());
38 })
39 ;
40
41 assert(false);
42 return *result;
43 }
44
45 //[named_override
46 template<typename T>
47 class positive_unary_pack
48 #define BASES public generic_unary_pack<T>
49 : BASES
50 {
51 public:
52 typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types;
53 #undef BASES
54
55 // BOOST_CONTRACT_OVERRIDE(_1) would generate reserved name `override__1`.
BOOST_CONTRACT_NAMED_OVERRIDE(override1,_1)56 BOOST_CONTRACT_NAMED_OVERRIDE(override1, _1) // Generate `override1`.
57
58 virtual void _1(T const& value, boost::contract::virtual_* v = 0)
59 /* override */ {
60 // Use `override1` generated by BOOST_CONTRACT_NAMED_OVERRIDE above.
61 boost::contract::check c = boost::contract::public_function<override1>(
62 v,
63 static_cast<void (positive_unary_pack::*)(T const&,
64 boost::contract::virtual_*)>(&positive_unary_pack::_1),
65 this,
66 value
67 )
68 .precondition([&] {
69 BOOST_CONTRACT_ASSERT(value > 0);
70 })
71 ;
72 value1_ = value;
73 }
74
75 /* ... */
76 //]
77
_1(boost::contract::virtual_ * v=0) const78 virtual T _1(boost::contract::virtual_* v = 0) const /* override */ {
79 T result; // Class default constructor already used T's default ctor.
80 boost::contract::check c = boost::contract::public_function<override1>(
81 v,
82 result,
83 static_cast<T (positive_unary_pack::*)(boost::contract::virtual_*)
84 const>(&positive_unary_pack::_1),
85 this
86 )
87 .postcondition([&] (T const& result) {
88 BOOST_CONTRACT_ASSERT(result > 0);
89 })
90 ;
91 return result = value1_;
92 }
93
94 private:
95 T value1_;
96 };
97
main()98 int main() {
99 positive_unary_pack<int> u;
100 u._1(123);
101 assert(u._1() == 123);
102 return 0;
103 }
104
105