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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_name_list
#include <boost/contract.hpp>
#include <string>
#include <vector>
#include <algorithm>
#include <cassert>
// List of names.
class name_list {
friend class boost::contract::access;
void invariant() const {
BOOST_CONTRACT_ASSERT(count() >= 0); // Non-negative count.
}
public:
/* Creation */
// Create an empty list.
name_list() {
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(count() == 0); // Empty list.
})
;
}
// Destroy list.
virtual ~name_list() {
// Check invariants.
boost::contract::check c = boost::contract::destructor(this);
}
/* Basic Queries */
// Number of names in list.
int count() const {
// Check invariants.
boost::contract::check c = boost::contract::public_function(this);
return names_.size();
}
// Is name in list?
bool has(std::string const& name) const {
bool result;
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
// If empty, has not.
if(count() == 0) BOOST_CONTRACT_ASSERT(!result);
})
;
return result = names_.cend() != std::find(names_.cbegin(),
names_.cend(), name);
}
/* Commands */
// Add name to list, if name not already in list.
virtual void put(std::string const& name,
boost::contract::virtual_* v = 0) {
boost::contract::old_ptr<bool> old_has_name =
BOOST_CONTRACT_OLDOF(v, has(name));
boost::contract::old_ptr<int> old_count =
BOOST_CONTRACT_OLDOF(v, count());
boost::contract::check c = boost::contract::public_function(v, this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(!has(name)); // Not already in list.
})
.postcondition([&] {
if(!*old_has_name) { // If-guard allows to relax subcontracts.
BOOST_CONTRACT_ASSERT(has(name)); // Name in list.
BOOST_CONTRACT_ASSERT(count() == *old_count + 1); // Inc.
}
})
;
names_.push_back(name);
}
private:
std::vector<std::string> names_;
};
class relaxed_name_list
#define BASES public name_list
: BASES
{
friend class boost::contract::access;
typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types; // Subcontracting.
#undef BASES
BOOST_CONTRACT_OVERRIDE(put);
public:
/* Commands */
// Add name to list, or do nothing if name already in list (relaxed).
void put(std::string const& name,
boost::contract::virtual_* v = 0) /* override */ {
boost::contract::old_ptr<bool> old_has_name =
BOOST_CONTRACT_OLDOF(v, has(name));
boost::contract::old_ptr<int> old_count =
BOOST_CONTRACT_OLDOF(v, count());
boost::contract::check c = boost::contract::public_function<
override_put>(v, &relaxed_name_list::put, this, name)
.precondition([&] { // Relax inherited preconditions.
BOOST_CONTRACT_ASSERT(has(name)); // Already in list.
})
.postcondition([&] { // Inherited post. not checked given if-guard.
if(*old_has_name) {
// Count unchanged if name already in list.
BOOST_CONTRACT_ASSERT(count() == *old_count);
}
})
;
if(!has(name)) name_list::put(name); // Else, do nothing.
}
};
int main() {
std::string const js = "John Smith";
relaxed_name_list rl;
rl.put(js);
assert(rl.has(js));
rl.put(js); // OK, relaxed contracts allow calling this again (do nothing).
name_list nl;
nl.put(js);
assert(nl.has(js));
// nl.put(js); // Error, contracts do not allow calling this again.
return 0;
}
//]
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