72 lines
1.8 KiB
C++
72 lines
1.8 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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//[mitchell02_counter
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#ifndef COUNTER_HPP_
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#define COUNTER_HPP_
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#include "../observer/subject.hpp"
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#include <boost/contract.hpp>
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class counter
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#define BASES public subject
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: BASES
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{
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friend class boost::contract::access;
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typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types;
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#undef BASES
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public:
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/* Creation */
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// Construct counter with specified value.
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explicit counter(int a_value = 10) : value_(a_value) {
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boost::contract::check c = boost::contract::constructor(this)
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.postcondition([&] {
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BOOST_CONTRACT_ASSERT(value() == a_value); // Value set.
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})
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;
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}
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// Destroy counter.
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virtual ~counter() {
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// Could have omitted contracts here (nothing to check).
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boost::contract::check c = boost::contract::destructor(this);
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}
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/* Queries */
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// Current counter value.
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int value() const {
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// Could have omitted contracts here (nothing to check).
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boost::contract::check c = boost::contract::public_function(this);
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return value_;
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}
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/* Commands */
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// Decrement counter value.
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void decrement() {
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boost::contract::old_ptr<int> old_value = BOOST_CONTRACT_OLDOF(value());
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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(value() == *old_value - 1); // Decrement.
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})
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;
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--value_;
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notify(); // Notify all attached observers.
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}
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private:
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int value_;
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};
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#endif // #include guard
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//]
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