78 lines
1.9 KiB
C++
78 lines
1.9 KiB
C++
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// Copyright (C) 2008-2018 Lorenzo Caminiti
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// Distributed under the Boost Software License, Version 1.0 (see accompanying
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// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
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// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
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#include <boost/contract.hpp>
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#include <limits>
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#include <cassert>
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//[private_protected
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class counter {
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protected: // Protected functions use `function()` (like non-members).
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void set(int n) {
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boost::contract::check c = boost::contract::function()
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.precondition([&] {
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BOOST_CONTRACT_ASSERT(n <= 0);
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})
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.postcondition([&] {
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BOOST_CONTRACT_ASSERT(get() == n);
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})
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;
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n_ = n;
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}
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private: // Private functions use `function()` (like non-members).
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void dec() {
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boost::contract::old_ptr<int> old_get = BOOST_CONTRACT_OLDOF(get());
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boost::contract::check c = boost::contract::function()
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.precondition([&] {
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BOOST_CONTRACT_ASSERT(
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get() + 1 >= std::numeric_limits<int>::min());
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})
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.postcondition([&] {
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BOOST_CONTRACT_ASSERT(get() == *old_get - 1);
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})
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;
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set(get() - 1);
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}
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int n_;
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/* ... */
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//]
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public:
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int get() const {
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int result;
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boost::contract::check c = boost::contract::public_function(this)
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.postcondition([&] {
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BOOST_CONTRACT_ASSERT(result <= 0);
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BOOST_CONTRACT_ASSERT(result == n_);
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})
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;
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return result = n_;
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}
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counter() : n_(0) {} // Should contract constructor and destructor too.
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void invariant() const {
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BOOST_CONTRACT_ASSERT(get() <= 0);
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}
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friend int main();
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};
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int main() {
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counter cnt;
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assert(cnt.get() == 0);
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cnt.dec();
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assert(cnt.get() == -1);
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return 0;
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}
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