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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
//[mitchell02_dictionary
#include <boost/contract.hpp>
#include <utility>
#include <map>
#include <cassert>
template<typename K, typename T>
class dictionary {
friend class boost::contract::access;
void invariant() const {
BOOST_CONTRACT_ASSERT(count() >= 0); // Non-negative count.
}
public:
/* Creation */
// Create empty dictionary.
dictionary() {
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(count() == 0); // Empty.
})
;
}
// Destroy dictionary.
virtual ~dictionary() {
// Check invariants.
boost::contract::check c = boost::contract::destructor(this);
}
/* Basic Queries */
// Number of key entries.
int count() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return items_.size();
}
// Has entry for key?
bool has(K const& key) const {
bool result;
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
// Empty has no key.
if(count() == 0) BOOST_CONTRACT_ASSERT(!result);
})
;
return result = (items_.find(key) != items_.end());
}
// Value for a given key.
T const& value_for(K const& key) const {
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(has(key)); // Has key.
})
;
// Find != end because of precondition (no defensive programming).
return items_.find(key)->second;
}
/* Commands */
// Add value of a given key.
void put(K const& key, T const& value) {
boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(!has(key)); // Has not key already.
})
.postcondition([&] {
BOOST_CONTRACT_ASSERT(count() == *old_count + 1); // Count inc.
BOOST_CONTRACT_ASSERT(has(key)); // Has key.
// Value set for key.
BOOST_CONTRACT_ASSERT(value_for(key) == value);
})
;
items_.insert(std::make_pair(key, value));
}
// Remove value for given key.
void remove(K const& key) {
boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(has(key)); // Has key.
})
.postcondition([&] {
BOOST_CONTRACT_ASSERT(count() == *old_count - 1); // Count dec.
BOOST_CONTRACT_ASSERT(!has(key)); // Has not key.
})
;
items_.erase(key);
}
private:
std::map<K, T> items_;
};
int main() {
std::string const js = "John Smith";
dictionary<std::string, int> ages;
assert(!ages.has(js));
ages.put(js, 23);
assert(ages.value_for(js) == 23);
ages.remove(js);
assert(ages.count() == 0);
return 0;
}
//]
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