ceph/src/boost/libs/contract/example/features/named_override.cpp

   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>
  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>
  33 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`.
  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
  78     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
  98 int main() {
  99     positive_unary_pack<int> u;
 100     u._1(123);
 101     assert(u._1() == 123);
 102     return 0;
 103 }
 104