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- // Copyright (C) 2008-2018 Lorenzo Caminiti
- // Distributed under the Boost Software License, Version 1.0 (see accompanying
- // file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
- // See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
- #include <boost/contract.hpp>
- #include <boost/config.hpp>
- #include <cassert>
-
- #ifdef BOOST_GCC // G++ does not support static union members yet.
- int instances_ = 0;
- #endif
- //[union
- union positive {
- public:
- static void static_invariant() { // Static class invariants (as usual).
- BOOST_CONTRACT_ASSERT(instances() >= 0);
- }
-
- void invariant() const { // Class invariants (as usual).
- BOOST_CONTRACT_ASSERT(i_ > 0);
- BOOST_CONTRACT_ASSERT(d_ > 0);
- }
- // Contracts for constructor, as usual but...
- explicit positive(int x) : d_(0) {
- // ...unions cannot have bases so constructor preconditions here.
- boost::contract::constructor_precondition<positive> pre([&] {
- BOOST_CONTRACT_ASSERT(x > 0);
- });
- boost::contract::old_ptr<int> old_instances =
- BOOST_CONTRACT_OLDOF(instances());
- boost::contract::check c = boost::contract::constructor(this)
- .postcondition([&] {
- { int y; get(y); BOOST_CONTRACT_ASSERT(y == x); }
- BOOST_CONTRACT_ASSERT(instances() == *old_instances + 1);
- })
- ;
- i_ = x;
- ++instances_;
- }
-
- // Contracts for destructor (as usual).
- ~positive() {
- boost::contract::old_ptr<int> old_instances =
- BOOST_CONTRACT_OLDOF(instances());
- boost::contract::check c = boost::contract::destructor(this)
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(instances() == *old_instances - 1);
- })
- ;
- --instances_;
- }
-
- // Contracts for public function (as usual, but no virtual or override).
- void get(int& x) const {
- boost::contract::check c = boost::contract::public_function(this)
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(x > 0);
- })
- ;
-
- x = i_;
- }
- // Contracts for static public function (as usual).
- static int instances() {
- boost::contract::check c = boost::contract::public_function<positive>();
- return instances_;
- }
- private:
- int i_;
- double d_;
-
- /* ... */
- //]
- public:
- explicit positive(double x) : d_(0) {
- // Unions cannot have bases so constructor preconditions here.
- boost::contract::constructor_precondition<positive> pre([&] {
- BOOST_CONTRACT_ASSERT(x > 0);
- });
- boost::contract::old_ptr<int> old_instances =
- BOOST_CONTRACT_OLDOF(instances());
- boost::contract::check c = boost::contract::constructor(this)
- .postcondition([&] {
- { double y; get(y); BOOST_CONTRACT_ASSERT(y == x); }
- BOOST_CONTRACT_ASSERT(instances() == *old_instances + 1);
- })
- ;
- d_ = x;
- ++instances_;
- }
-
- void get(double& x) const {
- boost::contract::check c = boost::contract::public_function(this)
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(x > 0);
- })
- ;
-
- x = d_;
- }
- #ifndef BOOST_GCC // G++ does not support static union members yet.
- static int instances_;
- #endif
- };
- #ifndef BOOST_GCC // G++ does not support static union members yet.
- int positive::instances_ = 0;
- #endif
- int main() {
- {
- positive p(123);
- assert(p.instances() == 1);
- { int y = -456; p.get(y); assert(y == 123); }
- positive q(1.23);
- assert(q.instances() == 2);
- { double y = -4.56; q.get(y); assert(y == 1.23); }
- }
- assert(positive::instances() == 0);
- return 0;
- }
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