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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 <limits>
- #include <cassert>
- //[private_protected
- class counter {
- protected: // Protected functions use `function()` (like non-members).
- void set(int n) {
- boost::contract::check c = boost::contract::function()
- .precondition([&] {
- BOOST_CONTRACT_ASSERT(n <= 0);
- })
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(get() == n);
- })
- ;
- n_ = n;
- }
- private: // Private functions use `function()` (like non-members).
- void dec() {
- boost::contract::old_ptr<int> old_get = BOOST_CONTRACT_OLDOF(get());
- boost::contract::check c = boost::contract::function()
- .precondition([&] {
- BOOST_CONTRACT_ASSERT(
- get() + 1 >= std::numeric_limits<int>::min());
- })
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(get() == *old_get - 1);
- })
- ;
- set(get() - 1);
- }
-
- int n_;
-
- /* ... */
- //]
- public:
- int get() const {
- int result;
- boost::contract::check c = boost::contract::public_function(this)
- .postcondition([&] {
- BOOST_CONTRACT_ASSERT(result <= 0);
- BOOST_CONTRACT_ASSERT(result == n_);
- })
- ;
- return result = n_;
- }
- counter() : n_(0) {} // Should contract constructor and destructor too.
-
- void invariant() const {
- BOOST_CONTRACT_ASSERT(get() <= 0);
- }
- friend int main();
- };
- int main() {
- counter cnt;
- assert(cnt.get() == 0);
- cnt.dec();
- assert(cnt.get() == -1);
- return 0;
- }
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